Physiological and technological considerations for optimising mass algal cultures

The successful coupling between physiology andtechnology is central to the success of algalbiotechnology. Imperative is a proper understandingof the variables and their impacts on biomass and/orbiocompound production. The crux lies inphotosynthesis and the capturing of light energy atthe optimal rate for eventual maximal photochemistry(biosynthesis). It is in the hands of algalbiotechnologists to understand the dynamics andregulatory mechanisms of especially PSII (photosystemII) activity in order to advance this technologyfurther. Biophysical and technological optimisationand design aimed at maximising photon flux capture aresome of the avenues that needs be pursued. This needsto be augmented by molecular, biochemical andphysiological inputs. Unfortunately detailedsystematic analyses of the variables, theirinteraction and possible synergism have rarely beendone. The debate regarding the merits andproductivity in closed, either plate or tubular,vertical or horizontal, and open pond reactors need tobe resolved. Exciting developments regarding onlinemeasurements and feedback control for optimalproductivities are part of the solutions andapproaches that need to be followed. Multistagesystems that not only utilise autotrophic growth andstress components, but also combinedautotrophic/heterotrophic systems could providesolutions to specific production requirements. Theseand other important issues are addressed in theoverview. The challenges facing algalbiotechnologists and future research needs are also discussed.     

Product formation kinetics in genetically modified <Emphasis Type="Italic">E. coli </Emphasis>bacteria: inclusion body formation

A data-driven model is presented that can serve two important purposes. First, the specific growth rate and the specific product formation rate are determined as a function of time and thus the dependency of the specific product formation rate from the specific biomass growth rate. The results appear in form of trained artificial neural networks from which concrete values can easily be computed. The second purpose is using these results for online estimation of current values for the most important state variables of the fermentation process. One only needs online data of the total carbon dioxide production rate (tCPR) produced and an initial value x of the biomass, i.e., the size of the inoculum, for model evaluation. Hence, given the inoculum size and online values of tCPR, the model can directly be employed as a softsensor for the actual value of the biomass, the product mass as well as the specific biomass growth rate and the specific product formation rate. In this paper the method is applied to fermentation experiments on the laboratory scale with an E. coli strain producing a recombinant protein that appears in form of inclusion bodies within the cells’ cytoplasm.     

Structure of the epithelium of the parasitic turbellaria Notenera ivanovi (Turbellaria: Fecampiida)

The ultrastructure of the epithelium in Notentera ivanovi (Turbellaria, Fecampiida) has been studied. Notentera ivanovi lacks the digestive system but has a pad of the epidermal cells on the dorsal side of the body, which seems to be similar to the digestive epidermis on LM. Both the ventral and dorsal epithelium are cellular, ciliated and not insunk (fig. 1, a). The ultrastructure of the ventral and dorsal epithelium is similar in essential features. The cells bear abundant microvilli, cilia and are very rich in mitochondria, but the cytoplasm does not contain lysosomes and shows no other indications of phago- or pinocytosis. The basal membrane of epithelial cells forms deep invaginations (fig. 1, [symbol: see text]), partly with dilations (fig. 1, a; 2, a) containing the lamellated material (3, [symbol: see text]). In the basal part of the cells the numerous Golgi apparatus and rare cysternae of the smooth endoplasmic reticulum were observed (fig. 2, a, [symbol: see text]). The epithelium consists of several types of cells, which differ in the structure of secretory granules. The most abundant type of cells contains the granules with the rough-fibrillated content (fig. 1, a; 2, [symbol: see text]; 3, a). The cells of this type cover most part of the body. In some cells the content of such granules becomes condensed and electron-dense granules appear (fig. 3, a, [symbol: see text]). Another type of cells contains the giant granules with the rough-fibrillated content (fig. 3, [symbol: see text]). Third type of the secret is the granules with the finely fibrillated content which is ejected by exocytosis. The cells of the second and third types form a separate areas of the epithelium of the dorsal side of the body but occasionally were observed in the ventral epithelium too. The epithelium of N. ivanovi differs from that in Kronborgia by the abundance and diversity of secretory contents. The role of the epithelium in the digestion remains conjectural. It seems to be mainly the suckering tissue transporting the low molecular nutrients.     

Economic impacts of bio-refinery and resource cascading systems: an applied general equilibrium analysis for Poland

Due to more stringent energy and climate policies, it is expected that many traditional chemicals will be replaced by their biomass-based substitutes, bio-chemicals. These innovations, however, can influence land allocation since the demand for land dedicated to specific crops might increase. Moreover, it can have an influence on traditional agricultural production. In this paper, we use an applied general equilibrium framework, in which we include two different bio-refinery processes and incorporate so-called cascading mechanisms. The bio-refinery processes use grass, as one of the major inputs, to produce bio-nylon and propane-diol (1,3PDO) to substitute currently produced fossil fuel-based nylon and ethane-diol. We examine the impact of specific climate policies on the bioelectricity share in total electricity production, land allocation, and production quantities and prices of selected commodities. The novel technologies become competitive, with an increased stringency of climate policies. This switch, however, does not induce a higher share of bioelectricity. The cascade does stimulate the production of bioelectricity, but it induces more of a shift in inputs in the bioelectricity sector (from biomass to the cascaded bio-nylon and 1, 3PDO) than an increase in production level of bioelectricity. We conclude that dedicated biomass crops will remain the main option for bioelectricity production: the contribution of the biomass systems remains limited. Moreover, the bioelectricity sector looses a competition for land for biomass production with bio-refineries.     

Thermodynamic approach to biomass distribution in ecological systems

In the derivation of the biomass distribution function for an ecological population critical use is made of an energetic constraint on the maximization of biomass diversity. The nature of this constraint is explored in detail using Kleiber's relation σ(m)=cm ^γ between animal metabolic rate σ(m) and body weightm in conjuction with the Prigogine-Wiame thermodynamic paradigm for specific entropy production in biological stationary states. These two inputs fix the energetic constraint on the maximization of biomass diversity to be the constancy of the mean metabolic rate of the ecosystem. The resulting biomass distribution function is tested against observational data.     

Ultrastructure of epithelium and ciliary receptors in the parasitic turbellarian Urastoma cyprinae (Turbellaria, "Prolecithophora") and position of the species within Platyhelminthes

Ultrastructure of the epithelium of adult and juvenile Urastoma cyprinae has been studied. The epithelium of both adult and juvenile worms is cellular, ciliated and bears numerous microvilli. The cytoplasm is rich in large, numerous epitheliosomes of two types--electron-dense and with fibrillated content (fig. 1, a, [symbol: see text]; 2, a-[symbol: see text]). Besides large secrete granules small membrane-bounded vesicles were observed (fig. 2, a-[symbol: see text]). In juvenile worms the dense epitheliosomes are less abundant and the fibrillated content in the second type of granules has a different structure: the fibrils are very thin and more densely packed forming the structures of the less electron density (fig. 3, a, [symbol: see text], [symbol: see text] 1). The membrane-bounded vesicles in the epithelium of juvenile worms were not observed. All types of secrete are ejected by exocytosis (fig. 2, [symbol: see text]; 3, [symbol: see text], [symbol: see text]). The ultrastructure of the epithelium in juvenile U. cyprinae is strongly similar to that in parasitic turbellarian Kronborgia, especially to the epithelium in a male and a larva. The basal lamina consists of tree layers and forms numerous deep infoldings into the epithelium (fig. 1, a; 2, a; 3, a, [symbol: see text], [symbol: see text]). The basement membrane projects deep and numerous invaginations into the epithelium which may almost reach the apical membrane (fig. 1, a; 2, a, [symbol: see text], [symbol: see text]; 3, [symbol: see text]). Mitochondria are large and situated mainly near the projections of the basement membrane (fig. 2, [symbol: see text]-[symbol: see text]; 3, [symbol: see text]). Such ultrastructure implies an intensive process of the transmembrane transfer of the dissolved organic substances from the sea water. The same structures were found in the epithelium of Kronborgia. Uptake of organic compounds through the epithelium in the common ancestors of Urastoma and Kronborgia could be the preadaptation to the endoparasitic mode of life in Fecampiida. The differencies in ultrastructure of epithelium in U. cyprinae from the White Sea and from Mediterranean Sea (Noury-Sra?ri e. a., 1990) may be explained by the differences in the method of fixation or by the parasitizing the another host--the mollusk Mytilus galloprovincialis. The ciliary receptors of five types were revealed in U. cyprinae (fig. 3, e, [symbol: see text]; 4; 5; 6). They differ in the shape and length of the ciliary rootlets and in the content of the nerve processes. All receptors lack of the real collars typical for the receptors of Neodermata. Urastoma is most close to the Neodermata amond parasitic turbellarians studied thus far, and the absence of collars in receptors of this species testifies that the collars are the veritable synapomorphy of the Neodermata. The diversity in the ultrastructure and possible functions of receptors correspond to the complicated adaptations of this species. The modern molecular data as well as the ultrastructural evidence attest that parasitic turbellarians of the genera Urastoma, Genostoma and Ichthyophaga are relatives and cannot be included in any turbellarian order known. Therefore Urastoma, Genostoma and Ichthyophaga have been erected in the separate order Urastomida ord. nov. The diagnosis of the new order is given.     

Herbivore influence on soil microbial biomass and nitrogen mineralization in a northern grassland ecosystem: Yellowstone National Park

Microorganisms are largely responsible for soil nutrient cycling and energy flow in terrestrial ecosystems. Although soil microorganisms are affected by topography and grazing, little is known about how these two variables may interact to influence microbial processes. Even less is known about how these variables influence microorganisms in systems that contain large populations of free-roaming ungulates. In this study, we compared microbial biomass size and activity, as measured by in situ net N mineralization, inside and outside 35- to 40-year exclosures across a topographic gradient in northern Yellowstone National Park. The objective was to determine the relative effect of topography and large grazers on microbial biomass and nitrogen mineralization. Microbial C and N varied by almost an order of magnitude across sites. Topographic depressions that contained high plant biomass and fine-textured soils supported the greatest microbial biomass. We found that plant biomass accurately predicted microbial biomass across our sites suggesting that carbon inputs from plants constrained microbial biomass. Chronic grazing neither depleted soil C nor reduced microbial biomass. We hypothesize that microbial populations in grazed grasslands are sustained mainly by inputs of labile C from dung deposition and increased root turnover or root exudation beneath grazed plants. Mineral N fluxes were affected more by grazing than topography. Net N mineralization rates were highest in grazed grassland and increased from dry, unproductive to mesic, highly productive communities. Overall, our results indicate that topography mainly influences microbial biomass size, while mineral N fluxes (microbial activity) are affected more by grazing in this grassland ecosystem. Received: 4 June 1997 / Accepted: 16 December 1997     

Modeling of polygalacturonase enzyme activity and biomass production by <Emphasis Type="Italic">Aspergillus sojae</Emphasis> ATCC 20235

Aspergillus sojae, which is used in the making of koji, a characteristic Japanese food, is a potential candidate for the production of polygalacturonase (PG) enzyme, which of a major industrial significance. In this study, fermentation data of an A. sojae system were modeled by multiple linear regression (MLR) and artificial neural network (ANN) approaches to estimate PG activity and biomass. Nutrient concentrations, agitation speed, inoculum ratio and final pH of the fermentation medium were used as the inputs of the system. In addition to nutrient conditions, the final pH of the fermentation medium was also shown to be an effective parameter in the estimation of biomass concentration. The ANN parameters, such as number of hidden neurons, epochs and learning rate, were determined using a statistical approach. In the determination of network architecture, a cross-validation technique was used to test the ANN models. Goodness-of-fit of the regression and ANN models was measured by the R ² of cross-validated data and squared error of prediction. The PG activity and biomass were modeled with a 5-2-1 and 5-9-1 network topology, respectively. The models predicted enzyme activity with an R ² of 0.84 and biomass with an R ² value of 0.83, whereas the regression models predicted enzyme activity with an R ² of 0.84 and biomass with an R ² of 0.69.     

Solid substrate cultivation of Gibberella fujikuroi on an inert support

Growth of Gibberella fujikuroi on Amberlite, an inert support, and gibberellic acid (GA₃) production was studied in glass columns under different conditions of temperature and water activity (a_w). Maximum biomass concentration and GA₃ production were respectively 40 (mg/g inert support) and 0.73 (mg/g inert support). While high specific growth rates were obtained, low initial nitrogen resulted in low biomass concentrations. Maximum GA₃ (31°C, a_w=0.985) was not produced by the maximum concentration of biomass (25°C, a_w=0.992). Peaks in the rate curves of either outlet gas, CO₂ or O₂, occurred on exhaustion of urea indicating, for future works, just when to feed the culture additional nitrogen.     

Time‐dependent climate impact of a bioenergy system – methodology development and application to Swedish conditions

The area of dedicated energy crops is expected to increase in Sweden. This will result in direct land use changes, which may affect the carbon stocks in soil and biomass, as well as yield levels and the use of inputs. Carbon dioxide (CO₂) fluxes of biomass are often not considered when calculating the climate impact in life cycle assessments (LCA) assuming that the CO₂ released at combustion has recently been captured by the biomass in question. With the extended time lag between capture and release of CO₂ inherent in many perennial bioenergy systems, the relation between carbon neutrality and climate neutrality may be questioned. In this paper, previously published methodologies and models are combined in a methodological framework that can assist LCA practitioners in interpreting the time‐dependent climate impact of a bioenergy system. The treatment of carbon differs from conventional LCA practice in that no distinction is made between fossil and biogenic carbon. A time‐dependent indicator is used to enable a representation of the climate impact that is not dependent on the choice of a specific characterization time horizon or time of evaluation and that does not use characterization factors, such as global warming potential and global temperature potential. The indicator used to aid in the interpretation phase of this paper is global mean surface temperature change (ΔT_s(n)). A theoretical system producing willow for district heating was used to study land use change effects depending on previous land use and variations in the standing biomass carbon stocks. When replacing annual crops with willow this system presented a cooling contribution to ΔT_s(n). However, the first years after establishing the willow plantation it presented a warming contribution to ΔT_s(n). This behavior was due mainly to soil organic carbon (SOC) variation. A rapid initial increase in standing biomass counteracted the initial SOC loss.     

Long-chain acylhomoserine lactones increase the anoxic ammonium oxidation rate in an OLAND biofilm

The oxygen-limited autotrophic nitrification/denitrification (OLAND) process comprises one-stage partial nitritation and anammox, catalyzed by aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB), respectively. The goal of this study was to investigate whether quorum sensing influences anoxic ammonium oxidation in an OLAND biofilm, with AnAOB colonizing 13% of the biofilm, as determined with fluorescent in situ hybridization (FISH). At high biomass concentrations, the specific anoxic ammonium oxidation rate of the OLAND biofilm significantly increased with a factor of 1.5 ± 0.2 compared to low biomass concentrations. Supernatant obtained from the biofilm showed no ammonium-oxidizing activity on itself, but its addition to low OLAND biomass concentrations resulted in a significant activity increase of the biomass. In the biofilm supernatant, the presence of long-chain acylhomoserine lactones (AHLs) was shown using the reporter strain Chromobacterium violaceum CV026, and one specific AHL, N-dodecanoyl homoserine lactone (C₁₂-HSL), was identified via LC-MS/MS. Furthermore, C₁₂-HSL was detected in an AnAOB-enriched community, but not in an AerAOB-enriched community. Addition of C₁₂-HSL to low OLAND biomass concentrations resulted in a significantly higher ammonium oxidation rate (p < 0.05). To our knowledge, this is the first report demonstrating that AHLs enhance the anoxic ammonium oxidation process. Future work should confirm which species are responsible for the in situ production of C₁₂-HSL in AnAOB-based applications.     

Soil [N] modulates soil C cycling in CO2‐fumigated tree stands: a meta‐analysis

Under elevated atmospheric CO₂ concentrations, soil carbon (C) inputs are typically enhanced, suggesting larger soil C sequestration potential. However, soil C losses also increase and progressive nitrogen (N) limitation to plant growth may reduce the CO₂ effect on soil C inputs with time. We compiled a data set from 131 manipulation experiments, and used meta‐analysis to test the hypotheses that: (1) elevated atmospheric CO₂ stimulates soil C inputs more than C losses, resulting in increasing soil C stocks; and (2) that these responses are modulated by N. Our results confirm that elevated CO₂ induces a C allocation shift towards below‐ground biomass compartments. However, the increased soil C inputs were offset by increased heterotrophic respiration (Rh), such that soil C content was not affected by elevated CO₂. Soil N concentration strongly interacted with CO₂ fumigation: the effect of elevated CO₂ on fine root biomass and –production and on microbial activity increased with increasing soil N concentration, while the effect on soil C content decreased with increasing soil N concentration. These results suggest that both plant growth and microbial activity responses to elevated CO₂ are modulated by N availability, and that it is essential to account for soil N concentration in C cycling analyses.     

A long‐term nitrogen fertilizer gradient has little effect on soil organic matter in a high‐intensity maize production system

Global maize production alters an enormous soil organic C (SOC) stock, ultimately affecting greenhouse gas concentrations and the capacity of agroecosystems to buffer climate variability. Inorganic N fertilizer is perhaps the most important factor affecting SOC within maize‐based systems due to its effects on crop residue production and SOC mineralization. Using a continuous maize cropping system with a 13 year N fertilizer gradient (0–269 kg N ha^?1 yr^?1) that created a large range in crop residue inputs (3.60–9.94 Mg dry matter ha^?1 yr^?1), we provide the first agronomic assessment of long‐term N fertilizer effects on SOC with direct reference to N rates that are empirically determined to be insufficient, optimum, and excessive. Across the N fertilizer gradient, SOC in physico‐chemically protected pools was not affected by N fertilizer rate or residue inputs. However, unprotected particulate organic matter (POM) fractions increased with residue inputs. Although N fertilizer was negatively linearly correlated with POM C/N ratios, the slope of this relationship decreased from the least decomposed POM pools (coarse POM) to the most decomposed POM pools (fine intra‐aggregate POM). Moreover, C/N ratios of protected pools did not vary across N rates, suggesting little effect of N fertilizer on soil organic matter (SOM) after decomposition of POM. Comparing a N rate within 4% of agronomic optimum (208 kg N ha^?1 yr^?1) and an excessive N rate (269 kg N ha^?1 yr^?1), there were no differences between SOC amount, SOM C/N ratios, or microbial biomass and composition. These data suggest that excessive N fertilizer had little effect on SOM and they complement agronomic assessments of environmental N losses, that demonstrate N₂O and NO₃ emissions exponentially increase when agronomic optimum N is surpassed.     

Effect of soil microorganisms and labile C availability on soil respiration in response to litter inputs in forest ecosystems: A meta‐analysis

Litter inputs can influence soil respiration directly through labile C availability and, indirectly, through the activity of soil microorganisms and modifications in soil microclimate; however, their relative contributions and the magnitude of any effect remain poorly understood. We synthesized 66 recently published papers on forest ecosystems using a meta‐analysis approach to investigate the effect of litter inputs on soil respiration and the underlying mechanisms involved. Our results showed that litter inputs had a strong positive impact on soil respiration, labile C availability, and the abundance of soil microorganisms, with less of an impact related to soil moisture and temperature. Overall, soil respiration was increased by 36% and 55%, respectively, in response to natural and doubled litter inputs. The increase in soil respiration induced by litter inputs showed a tendency for coniferous forests (50.7%)> broad‐leaved forests (41.3%)> mixed forests (31.9%). This stimulation effect also depended on stand age with 30‐ to 100‐year‐old forests (53.3%) and ≥100‐year‐old forests (50.2%) both 1.5 times larger than ≤30‐year‐old forests (34.5%). Soil microbial biomass carbon and soil dissolved organic carbon increased by 21.0%‐33.6% and 60.3%‐87.7%, respectively, in response to natural and doubled litter inputs, while soil respiration increased linearly with corresponding increases in soil microbial biomass carbon and soil dissolved organic carbon. Natural and doubled litter inputs increased the total phospholipid fatty acid (PLFA) content by 6.6% and 19.7%, respectively, but decreased the fungal/bacterial PLFA ratio by 26.9% and 18.7%, respectively. Soil respiration also increased linearly with increases in total PLFA and decreased linearly with decreases in the fungal/bacterial PLFA ratio. The contribution of litter inputs to an increase in soil respiration showed a trend of total PLFA > fungal/bacterial PLFA ratio > soil dissolved organic carbon > soil microbial biomass carbon. Therefore, in addition to forest type and stand age, labile C availability and soil microorganisms are also important factors that influence soil respiration in response to litter inputs, with soil microorganisms being more important than labile C availability.     

Growth physiology and dimorphism of <Emphasis Type="Italic">Mucor circinelloides</Emphasis> (syn<Emphasis Type="Italic">. racemosus)</Emphasis> during submerged batch cultivation

Mucor circinelloides is being investigated as a possible host for the production of heterologous proteins. Thus, the environmental conditions defining the physiology and morphology of this dimorphic fungus have been investigated in submerged batch cultivation. The optimal conditions for growth of each form have been defined. Pure cultures of the multi-polar budding yeast form could be obtained under anaerobic conditions (with 70% N2/30% CO2 or 100% N2 as the sparge gas and without aeration). The highest maximum specific growth rate (0.30 h(-1)) was obtained in anaerobic cultivation, the yield of biomass on glucose (Y(SX)) was 0.12 (c-mole basis). A high maximum specific growth rate was obtained when the organism grew as the filamentous form under aerobic conditions (0.25 h(-1)), with a Y(SX) of 0.24 (c-mole basis). The maximum specific growth rates achieved are comparable to most industrial filamentous fungi under similar growth conditions. High levels of ethanol were observed with all growth conditions. The overriding effector of morphological development was found to be oxygen. In batch cultures it was therefore possible to induce the dimorphic shift by controlling the influent gas atmosphere. A specific growth rate of 0.19 h(-1) was maintained during the shift from the yeast to the filamentous form.     

Production of carbonyl reductase by Metschnikowia koreensis

A new strain of the yeast Metschnikowia koreensis was grown in shake flasks and a stirred bioreactor for the production of carbonyl reductase. The optimal conditions in the bioreactor for maximizing the biomass specific activity of the enzyme were found to be: a medium composed of glucose (20 g/L), peptone (5 g/L), yeast extract (5 g/L) and zinc sulfate (0.3g/L); the pH controlled at 7; the temperature controlled at 25 °C; an agitation speed of 500 rpm; and an aeration rate of 0.25 vvm. In the bioreactor, a biomass specific enzyme activity of 115.6 U/gDCW was obtained and the maximum biomass concentration was 15.3 gDCW/L. The biomass specific enzyme activity obtained in the optimized bioreactor culture was 11-fold higher than the best result achieved in shake flasks. The bioreactor culture afforded a 2.7-fold higher biomass concentration than could be attained in shake flasks.     

Dependence of morphology on agitation intensity in fed-batch cultures of Aspergillus oryzae and its implications for recombinant protein production

We previously reported that, although agitation conditions strongly affected mycelial morphology, such changes did not lead to different levels of recombinant protein production in chemostat cultures of Aspergillus oryzae (Amanullah et al., 1999). To extend this finding to another set of operating conditions, fed-batch fermentations of A. oryzae were conducted at biomass concentrations up to 34 g dry cell weight/L and three agitation speeds (525, 675, and 825 rpm) to give specific power inputs between 1 and 5 kWm(-3). Gas blending was used to control the dissolved oxygen level at 50% of air saturation except at the lowest speed where it fell below 40% after 60-65 h. The effects of agitation intensity on growth, mycelial morphology, hyphal tip activity, and recombinant protein (amyloglucosidase) production in fed-batch cultures were investigated. In the batch phase of the fermentations, biomass concentration, and AMG secretion increased with increasing agitation intensity. If in a run, dissolved oxygen fell below approximately 40% because of inadequate oxygen transfer associated with enhanced viscosity, AMG production ceased. As with the chemostat cultures, even though mycelial morphology was significantly affected by changes in agitation intensity, enzyme titers (AGU/L) under conditions of substrate limited growth and controlled dissolved oxygen of >50% did not follow these changes. Although the measurement of active tips within mycelial clumps was not considered, a dependency of the specific AMG productivity (AGU/g biomass/h) on the percentage of extending tips was found, suggesting that protein secretion may be a bottle-neck in this strain during fed-batch fermentations.     

Der Gesangsaufbau von Braunkehlchen(Saxicola rubetra) und Schwarzkehlchen(S. torquata) im Vergleich

Zusammenfassung Braunkehlchen und Schwarzkehlchen verfügen über ein großes individuelles Repertoire (über 100 Elementtypen), das sich in 12 gemeinsame Lautklassen gliedern läßt. In der Bevorzungung der einzelnen Klassen traten große individuelle Unterschiede auf. Das gesamte Repertoire beider Arten kann man in Strophenklassen einteilen, die nach Übereinstimmung der Anfangslaute oder ganzer Elementsequenzen definiert werden. Das Schwarzkehlchen singt meist mehrere Strophen der gleichen Klasse hintereinander, das Braunkehlchen wechselt die Strophenklasse nach jeder Strophe. Um den abwechslungsreichen Klangeindruck des Braunkehlchengesanges und den eher monotonen Eindruck des Schwarzkehlchengesanges näher zu bestimmen, wurde der Tonhöhenwechsel zwischen aufeinanderfolgenden Lauten quantitativ untersucht. Da die lineare Darstellung im Sonagrammbild nicht der akustischen Auflösung des menschlichen Gehörs entspricht, werden die Frequenzunterschiede in Quotienten umgerechnet und in Klassen eingeteilt. Die gebildeten Klassen sind zur Anschaulichkeit nach den in der Musik gebräuchlichen Intervallen benannt; sie stellen somit keinen reinen Melodieverlauf dar, sondern stehen für ganze Intervallbereiche, die benutzt werden. Beim Schwarzkehlchen finden sich insgesamt kleinere Intervalle als beim Braunkehlchen, welches sowohl größere Intervalle zwischen den Elementen bildet, als auch wesentlich mehr Elemente im unteren Frequenzbereich singt. Dadurch entsteht ein melodiöser Eindruck.

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Comparison of Whinchat's and Stonechat's songs(Saxicola rubetra, S. torquata)

Summary To study the organization and the species specific basic pattern of the whinchats' and stonechats' songs data from several birds in West Germany were compared to records made in different parts of Europe. Both species have a rather large repertoire, consisting of about 100 different utterances (see fig. 2). The repertoire can be classified in twelve common basic categories (see fig. 5). A high percentage of whistle-like structures occur in both species. However, there is a considerable variation in terms of the use of this categories in different individuals (see tab. 2). Phrases consisting of identical or similar sequences of elements are called song-type. Whinchats regularyly change the song-type from one phrase to another, whereas stonechats often repeat the same song-type in consecutive phrases (see fig. 4). Songs of whinchats sound melodious to human ears, compared to the more monotonous songs of the stonechats. To asses this quantitatively, the degrees between consecutive notes were studied: according to human auditory sensation a logarithmic rather than linear measurement was used. The quotients between the end of the preceeding and the beginning of the succeeding note were calculated (see fig. 7). The occurring quotients of frequency were classified; for reasons of clearness the resulting classes were named after the corresponding melodic intervals in music. In the stonechats' songs small melodic intervals in the range of the second degree mostly occur and larger melodic intervals are less frequent (see fig. 9). In the songs of whinchats no preferences for small melodic intervals appear and larger intervals (range of octave and larger) were used more frequently (see fig. 9). One of the fundamental differences between the two species is found in the arrangement patterns of similar vocal structures: whinchats sing within a larger frequency band (between 2,5 cps—8 cps) compared to the stonechats, which sing between 3 cps and 7 cps.

     

The boosted lipid accumulation in microalga <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> by a heterotrophy and nutrition-limitation transition cultivation regime

A model of heterotrophy and nutrition-limitation transition cultivation for efficient algal biomass and lipid production was proposed in this study, wherein sufficient robust heterotrophic-seed cells submitted into nitrogen-starvation induction for boosted lipid accumulation. The results demonstrated that heterotrophic-seed (HS) achieved specific growth rate of 1.35 day^?1 and biomass productivity of 1.93 mg/L/d, representing 6.42- and 32.16-fold, 2.01- and 2.75-fold more than that of photoautotrophic-seed (PS) and mixtrophic-seed (MS). Even though subsequent nutrition-limitation cultivation repressed the growth of HS, the overall lipid productivity caused by nitrogen-starvation was not offset by biomass loss. The most favorable lipid productivity (465.61 mg/L/d) of HS was 3.25 and 52.31 times higher than that of MS and PS. The high content of monounsaturated fatty acids (50.13%) over saturated and polyunsaturated fatty acids (totally 47.39%) in HS cells could provide superior oxidation stability and lower viscosity for biofuels generated from algal biomass feedstock. These findings suggested the feasibility of using heterotrophy and nutrition-limitation transition cultivation for enhancing the overall lipid productivity. Further, several critical enzymes (i.e. G3PDH, ME, and ACAD) were highly related to lipid accumulation and showed especially pronounced up-regulation or down-regulation expression in HS, which provide indications for shedding light on the molecular mechanisms of lipid accumulation and a prospective metabolic engineering for lipid production.