Heterotrophic production of Chlorella sp. TISTR 8990—biomass growth and composition under various production conditions

The green microalga Chlorella sp. TISTR 8990 was grown heterotrophically in the dark using various concentrations of a basal glucose medium with a carbon‐to‐nitrogen mass ratio of 29:1. The final biomass concentration and the rate of growth were highest in the fivefold concentrated basal glucose medium (25 g L^?1 glucose, 2.5 g L^?1 KNO₃) in batch operations. Improving oxygen transfer in the culture by increasing the agitation rate and decreasing the culture volume in 500‐mL shake flasks improved growth and glucose utilization. A maximum biomass concentration of nearly 12 g L^?1 was obtained within 4 days at 300 rpm, 30°C, with a glucose utilization of nearly 76% in batch culture. The total fatty acid (TFA) content of the biomass and the TFA productivity were 102 mg g^?1 and 305 mg L^?1 day^?1, respectively. A repeated fed‐batch culture with four cycles of feeding with the fivefold concentrated medium in a 3‐L bioreactor was evaluated for biomass production. The total culture period was 11 days. A maximum biomass concentration of nearly 26 g L^?1 was obtained with a TFA productivity of 223 mg L^?1 day^?1. The final biomass contained (w/w) 13.5% lipids, 20.8% protein and 17.2% starch. Of the fatty acids produced, 52% (w/w) were saturated, 41% were monounsaturated and 7% were polyunsaturated (PUFA). A low content of PUFA in TFA feedstock is required for producing high quality biodiesel. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1589–1600, 2017     

Utilization of metabolic scope in relation to feeding and activity by individual and grouped zebrafish, Brachydanio rerio (Hamilton-Buchanan)

Metabolic scope and its utilization in relation to feeding and activity were measured in individual and grouped zebrafish (weight range, 430–551 mg) at 24° C by respirometry. Mean maximum metabolic rate, induced by swimming to exhaustion, R_max(i), was 1223 (s.d. , 157) mg O₂, kg^?1 h^?1 for individuals. Standard metabolic rate, R_s. was 364 mg O₂ kg^?1 h^?1, as estimated by extrapolating to zero activity from measurements of unfed, spontaneously active individuals. Mean routine metabolic rate, R_rout, of individuals was 421 (s.d. , 58) mg O₂, kg_-1 h_-1. The mean voluntary maximum metabolic rate, R_max(v), following transfer of minimally exercised fish to the respirometer, was 1110 (s.d. , 83) mg O₂ kg ^?1 h^?1 for groups of six fish, and was not significantly different from the value measured for individuals, 1066 (s.d. , 122) mg O₂, kg^?1 h^?1. Grouped fish acclimated to the respirometer more slowly than individual fish and exhibited significantly higher R_rout, apparently a result of greater social interaction and activity in groups. Mean R_rout for groups was 560 (s.d. , 78) mg O₂, kg^?1 h^?1. While groups of zebrafish fed a ration of 5% wet body weight day^?1 exhibited consistently higher metabolic rates than fish fed rations of 2.5% wet body weight day^?1 the high ration group still used only a maximum of 77% of the metabolic scope. Zebrafish of the size studied do not appear to demonstrate a high degree of conflict in utilization of metabolic scope by different respiratory components. The metabolic rates measured for zebrafish are among the highest yet measured for fish of similar size and at similar temperatures.     

Anaerobic fermentation of woody biomass treated by various methods

Anaerobic fermentation was attempted to produce methane from the wood chip (Eucalyptus globulus). By the pretreatment of the wood chip using hot water with high temperature, NaOH, and steam explosion, the production of methane gas was enhanced. The pretreatment using steam explosion resulted in more amount of methane gas produced than the treatment using either hot water or 1% (w/w) NaOH with high temperature, and the steam explosion at a steam pressure of 25 atm and a steaming time of 3 min was the most effective for the methane production. The amount of methane gas produced depended on the ratio of weight of Klason lignin, a high molecular weight lignin, in the treated wood chip.     

Effect of oleic acid on the production of ethanol and fructose from glucose/fructose mixtures in an immobilized cell reactor

Saccharomyces cerevisiae ATCC 39859 was immobilized onto small cubes of wood to produce ethanol and very enriched fructose syrup from glucose/fructose mixtures through the selective fermentation of glucose. A maximum ethanol productivity of 21.9 g/l-h was attained from a feed containing 9.7% (w/v) glucose and 9.9% (w/v) fructose. An ethanol concentration, glucose conversion and fructose yield of 29.6 g/l, 62% and 99% were obtained, respectively. This resulted in a final fructose/glucose ratio of 2.7. At lower ethanol productivity levels the fructose/glucose ratio increases, as does the ethanol concentration in the effluent. The addition of 30 mg/l oleic acid to the medium increased the ethanol productivity and its concentration by 13% at a dilution rate of 0.74 h^?1.     

Poly(3-hydroxybutyrate) production by Cupriavidus necator using waste glycerol

Polyhydroxyalkanoates (PHAs) have been recognized as good substitutes for the non-biodegradable petrochemically produced polymers. However, their high (real or estimated) current production cost limits their industrial applications. This work exploits two strategies to enhance PHAs substitution potential: the increase in PHA volumetric productivity in high density cultures and the use of waste glycerol (GRP), a by-product from the biodiesel industry, as primary carbon source for cell growth and polymer synthesis. Cupriavidus necator DSM 545 was used to accumulate poly(3-hydroxybutyrate) (P(3HB)) from GRP and from commercial glycerol (PG) as control substrate. On PG, productivities between 0.6 g_PHB L^?1 h^?1 and 1.5 g_PHB L^?1 h^?1 were attained. The maximum cell DW was 82.5 g_DW L^?1, the P(3HB) content being 62%. When GRP was used, 68.8 g_DW L^?1 with a P(3HB) accumulation of 38% resulting in a final productivity of 0.84 g_PHB L^?1 h^?1 was obtained. By decreasing the biomass concentration at which accumulation was triggered, a productivity of 1.1 g_PHB L^?1 h^?1 (50% P(3HB), w/w) was attained using GRP. P(3HB) molecular weights (M_w) ranged from 7.9 × 10⁵ to 9.6 × 10⁵ Da.     

Spatial and temporal dynamics of diffusive methane emissions in the Okavango Delta,northern Botswana,Africa

Global warming is associated with the continued increase in the atmospheric concentrations of greenhouse gases; carbon dioxide, methane (CH₄) and nitrous oxide. Wetlands constitute the largest single natural source of atmospheric CH₄ in the world contributing between 100 and 231 Tg year^?1 to the total budget of 503–610 Tg year^?1, approximately 60 % of which is emitted from tropical wetlands. We conducted diffusive CH₄ emission measurements using static chambers in river channels, floodplains and lagoons in permanent and seasonal swamps in the Okavango Delta, Botswana. Diffusive CH₄ emission rates varied between 0.24 and 293 mg CH₄ m^?2 h^?1, with a mean (±SE) emission of 23.2 ± 2.2 mg CH₄ m^?2 h^?1 or 558 ± 53 mg CH₄ m^?2 day^?1. These emission rates lie within the range reported for other tropical wetlands. The emission rates were significantly higher (P < 0.007) in permanent than in seasonal swamps. River channels exhibited the highest average fluxes at 31.3 ± 5.4 mg CH₄ m^?2 h^?1 than in floodplains (20.4 ± 2.5 mg CH₄ m^?2 h^?1) and lagoons (16.9 ± 2.6 mg CH₄ m^?2 h^?1). Diffusive CH₄ emissions in the Delta were probably regulated by temperature since emissions were highest (20–300 mg CH₄ m^?2 h^?1) and lowest (0.2–3.0 mg m^?2 h^?1) during the warmer-rainy and cooler winter seasons, respectively. Surface water temperatures between December 2010 and January 2012 varied from 15.3 °C in winter to 33 °C in summer. Assuming mean inundation of 9,000 km², the Delta’s annual diffusive emission was estimated at 1.8 ± 0.2 Tg, accounting for 2.8 ± 0.3 % of the total CH₄ emission from global tropical wetlands.     

Tree ring responses to elevated CO2 and increased N deposition in Picea abies

Four- to seven-year-old spruce trees (Picea abies) were exposed to three CO₂ concentrations (280, 420 and 560 cm³ m^?3) and three rates of wet N deposition (0, 30 and 90 kg ha^?1 year^?1) for 3 years in a simulated montane forest climate. Six trees from each of six clones were grown in competition in each of nine 100 × 70 × 36 cm model ecosystems with nutrient-poor natural forest soil. Stem dises were analysed using X-ray densitometry. The radial stem increment was not affected by [CO₂] but increased with increasing rates of N deposition. Wood density was increased by [CO₂], but decreased by N deposition. Wood-starch concentration increased, and wood nitrogen concentration decreased with increasing [CO₂], but neither was affected by N deposition. The lignin concentration in wood was affected by neither [CO₂] nor N deposition. Our results suggest that, under natural growth conditions, rising atmospheric [CO₂] will not lead to enhanced radial stem growth of spruce, but atmospheric N deposition will, and in some regions is probably already doing so. Elevated [CO₂], however, will lead to denser wood unless this effect is compensated by massive atmospheric N deposition. If can be speculated that greater wood density under elevated [CO₂] may alter the mechanical properties of wood, and higher ratios of C/N and lignin/N in wood grown at elevated [CO₂] may affect nutrient cycles of forest ecosystems.     

Respiratory-cardiovascular physiology and chloroethane gill flux in the channel catfish, Ictalurus punctatus

A fish respirometer-metabolism chamber was used to obtain in vivo respiratory-cardiovascular and chloroethane gill flux data on transected channel catfish (Ictalurus punctatus). Methods used for spinal transection, attachment of an oral membrane (respiratory mast), placement and attachment of blood cannulas and urine catheters are described. Respiratory physiology, cardiac output and chemical extraction efficiencies for 1,1,2,2-tetrachloroethane (TCE), pentachloroethane (PCE), and hexachloroethane (HCE) were determined on 419–990 g catfish. The overall mean values (± s.d.) for ventilation volume (Q_v), effective respiratory volume (Q_w), oxygen consumption (Vo₂ and percentage utilization of oxygen (U) were 17-3 ±4–71 h^?1 kg^?1, 9·8±l·71 h^?1 kg^?1, 71·6±12·5mg h^?1 kg^?1, and 49± 10%, respectively, while cardiac output calculated via the Fick Method was 2·4±0·61 h^?1 kg^?1. Additional measurements were made on ventilation rate (V_r), total plasma protein, haematocrit (Hct), and urine volume; while both arterial and venous blood were analysed for pH, oxygen partial pressure (P02), carbon dioxide partial pressure (Pco₂), total oxygen (To₂), total carbon dioxide (Tco₂) and total ammonia (TAMM). Physiological measurements taken at 24 h were not significantly different from those taken at 48 h and indicated no deterioration of the in vivo preparation. All of these values agreed well with literature values on UTitransected channel catfish, except for Hct which was lower for cannulated animals used in this study. Overall, these data provide strong support for the use of transected channel catfish for in vivo collection of physiological and chemical gill flux data. The mean initial chemical extraction efficiencies for TCE, PCE and HCE were 41, 61 and 73%, respectively. Chemical clearances (Cl_X) for these same three chemicals were 5·9, 9·3 and 10·8 1 h^?1 kg^?1, respectively. The approximate 1: 1 relationship between effective respiratory volume (Q_w) and chemical clearance (Cl_x) indicated that branchial uptake of PCE and HCE was water flow-limited. Chemical gill flux observed for channel catfish and chloroethanes was similar to that observed for rainbow trout in previous studies and provided further support for the flow-limited model of chemical flux across fish gills.     

Biomimetic MXene Textures with Enhanced Light‐to‐Heat Conversion for Solar Steam Generation and Wearable Thermal Management

2D materials are of particular interest in light‐to‐heat conversion, yet challenges remain in developing a facile method to suppress their light reflection. Herein, inspired by the black scales of Bitis rhinoceros, a generalized approach via sequential thermal actuations to construct biomimetic 2D‐material nanocoatings, including Ti₃C₂T_x MXene, reduced graphene oxide (rGO), and molybdenum disulfide (MoS₂) is designed. The hierarchical MXene nanocoatings result in broadband light absorption (up to 93.2%), theoretically validated by optical modeling and simulations, and realize improved light‐to‐heat performance (equilibrium temperature of 65.4 °C under one‐sun illumination). With efficient light‐to‐heat conversion, the bioinspired MXene nanocoatings are next incorporated into solar steam‐generation devices and stretchable solar/electric dual‐heaters. The MXene steam‐generation devices require much lower solar‐thermal material loading (0.32 mg cm^?2) and still guarantee high steam‐generation performance (1.33 kg m^?2 h^?1) compared with other state‐of‐the‐art devices. Additionally, the mechanically deformed MXene structures enable the fabrication of stretchable and wearable heaters dual‐powered by sunlight and electricity, which are reversibly stretched and heated above 100 °C. This simple fabrication process with effective utilization of active materials promises its practical application value for multiple solar–thermal technologies.     

Measurements of aerobic metabolism of a school of horse mackerel at different swimming speeds

Oxygen consumption rates were measured in a school of 56 horse mackerel Trachurus trachurus while at rest and while swimming at steady sustained speeds. Resting values of 38.76 and 42.10mg O₂ kg^?1 h^?1 were measured in a sealed cylindrical tank (535 l) while observing that the fish school remained neutrally buoyant and inactive with only gentle pectoral fin movements and no swimming motion. The same school was trained to swim with projected light patterns within a 10-m diameter annular doughnut respirometer. The oxygen consumption increased from the resting level through 51 mg O₂ kg^?1 h^?1 at the slowest swimming speeds of 0.29 m s^?1 (0.95 L s^?1) to around 259 mg O₂ kg^?1 h^?1 at the higher measured swimming speed of 0.87 m s^?1 (2.82 L s^?1). The data fitted a curve where oxygen consumption rose in proportion to velocity to the power of 2.56 with the intercept at the resting level. The maximum sustained speed (80 min) of 1.12 m s^?1 (3.63 Ls^?1) was not achieved within the respirometer but corresponded to an estimated oxygen consumption of 458.33 mg O₂ kg^?1 h^?1 giving a scope for aerobic activity of 419.02 mg O₂ kg^?1 h^?1. At a speed of 0.87 m s^?1, there was a lower bound on the aerobic efficiency of at least 38% and at 1.12 m s^?1, the highest aerobic speed, of 40%. Sustained speeds swum in a curved path as here should be increased by 5% for a straight path giving a maximum sustained 80 min speed of 1.18 m s^?1.     

Continuous biodegradation of phenoxyalkanoate herbicides by Sphingomonas herbicidovorans MH in a PU-supplied bubble reactor

The continuous aerobic degradation of phenoxyalkanoate herbicides by Sphingomonas herbicidovorans MH was investigated in a bubble reactor filled with modified polyurethane-foam (PU 90/51) as a carrier for the adsorptive immobilization of the bacterial cells. The PU-foam was applied in the form of plates (5 × 10 × 10 mm) and the amount added was equivalent to a PU-load of 1.25% [w/v]. Strain MH is capable of detoxifying the dichloro-substituted phenoxyalkanoates 2,4-DP, 2,4-D and 2,4-DB and the methylchloro-substituted phenoxyalkanoates MCPA, MCPP and MCPB. Degradation of the respective substrate was followed by HPLC analyses and by determination of the chloride release. No intermediates of the degradation pathways or “dead end” products were detected by HPLC analyses. The PU-bubble reactor with immobilized 2,4-DP-pre-grown cells was run continuously at 30°C at the high dilution rate of D = 0.5h^?1 with 2,4-DP (0.2 g/l), and with subsequent changes to each of the other phenoxyalkanoates as a single substrate in the feed and with an intermittent return to 2,4-DP. Finally, after an intermediate substrate accumulation, 2,4-D, 2,4-DP, MCPA and MCPP could be degraded under the aforementioned conditions corresponding to a maximum degradation rate of Q_phen = 100 mg/l × h. In the case of 2,4-DB, a slightly reduced conversion rate of about 94% could be calculated. In contrast to these results, 0.2 g/l of the more recalcitrant MCPB could not be metabolized at this high dilution rate of D = 0.5 h^?1 by the biofilm of Sphingomonas herbicidovorans MH, but it was degradable at a reduced dilution rate of D = 0.25 h^?1. Complete detoxification of a stoichiometric mixture of the dichloro- and the methylchloro-substituted phenoxyalkanoates including MCPB, respectively, at a total concentration of 0.2 g/l was achieved at D = 0.25 h^?1, corresponding to a degradation rate of Q_tot = 50 mg/l × h. Finally, the efficiency of the PU-immobilized cells of Sphingomonas herbicidovorans MH in detoxifying mixtures of all six herbicides could be increased to Q_tot = 75 mg/l × h by the further addition of PU-foam particles corresponding to a final PU-load of 2.5% [w/v]. This PU-bubble reactor was successfully operated for more than 12 months to clean up synthetically concocted waste waters with fluctuations in phenoxyalkanoate concentration and composition.     

Batch and fed-batch fermentation of optically pure D (-) lactic acid from Kodo millet (Paspalum scrobiculatum) bran residue hydrolysate: growth and inhibition kinetic modeling

Abstract

A low-cost Kodo millet bran residue was utilized as feedstock for the production of D (?) lactic acid (DLA) using Lactobacillus delbrueckii NBRC3202 under anaerobic condition. Data culled from a series of batch fermentation processes with different initial Kodo millet bran residue hydrolysate (KMBRH) and DLA concentrations were used for kinetic model development. Both simulated and experimental data were in good agreement for cell growth, KMBRH utilization, and DLA formation. The values of kinetic constants specific growth rate, (μ_m = 0.17?h^?1); growth (α_P = 0.96?g.g^?1) and non-growth (β_P = 1.19?g.g^?1.h^?1) associated constant for DLA production and the maximum specific KMBRH utilization rate, (q_{G, max} = 1.18?g.g^?1.h^?1) were in good agreement with the literature reports. Kinetic analysis elucidated that L. delbrueckii growth was predominantly influenced by KMBRH limitation and highly sensitive to DLA inhibition. Fed-batch fermentation studies demonstrated the existence of substrate and product inhibition paving the scope for process intensification.     

Bimodal oxygen uptake in a freshwater air-breathing fish,Notopterus chitala

Measurements of bimodal oxygen uptake have been made in a freshwater air-breathing fish,Notopterus chitala at 29.0±1(S.D.)°C. xhe mean oxygen uptake from continuously flowing water without any access to air, was found to be 3.58±0.37 (S.E.) ml O₂ · h^?1 and 56.84+4.29 (S.E.) ml O₂ · kg^?1 · h^?1 for a fish weighing 66.92 + 11.27 (S.E.) g body weight. In still water with access to air, the mean oxygen uptake through the gills were recorded to be 2.49 ± 0.31 (S.E.) ml O₂ · h^?1 and 38.78 ± 1.92 (S.E.) ml O₂ · kg^?1 · h^?1 and through the accessory respiratory organs (swim-bladder) 6.04±0.87 (S.E.) ml O₂ · h^?1 and 92.32±2.91 (S.E.) ml O₂ · kg^?1 · h^?1 for a fish averaging 66.92±11.27 (S.E.) g. Out of the total oxygen uptake (131.10 ml O₂ · kg^?1 · h^?1), about 70% was obtained through the aerial route and the remainder 30% through the gills.     

Heterotrophic nitrification and aerobic denitrification by a novel Halomonas campisalis

A novel halophilic strain that could carry out heterotrophic nitrification and aerobic denitrification was isolated and named as Halomonas campisalis ha3. It removed inorganic nitrogen compounds (e.g. NO₃ ^?, NO₂ ^? and NH₄ ⁺) simultaneously, and grew well in the medium containing up to 20 % (w/v) NaCl. PCR revealed four genes in the genome of ha3 related to aerobic denitrification: napA, nirS, norB and nosZ. The optimal conditions for aerobic denitrification were pH 9.0, at 37 °C, with 4 % (w/v) NaCl and sodium succinate as carbon source. The nitrogen removal rate was 87.5 mg NO₃ ^?–N l^?1 h^?1. Therefore, this strain is a potential aerobic denitrifier for the treatment of saline wastewater.     

Effect of oxygen transfer rate on the composition of the pectolytic enzyme complex of Aspergillus niger

Optimal agitation and aeration conditions [assuring O₂ transfer rates (OTR) from 12 to 179 mmol L^?1 h^?1] were determined for pectin lyase (PL) synthesis of an Aspergillus niger strain. Components of the pectolytic enzyme complex were also investigated in order to determine whether their O₂ demand is identical with or different from that of pectin lyase. Should the latter be the case, a possibility would be given to produce enzyme complexes of different agitation and aeration conditions. According to our results, mycelium yield of Aspergillus niger attained a maximum at an OTR of 100 mmol L^?1 h^?1. The yields of the various pectolytic enzymes reached maxima at different OTRs. Pectin lyase production was the highest (0.555 µmol min^?1 mL^?1) at an OTR of 60 mmol L^?1 h^?1. Endopolygalacturonase (PG) production showed a maximum at the OTR of 49 mmol L^?1 h^?1 with a second peak at 100?135 mmol O₂ L^?1 h^?1. Pectin esterase (PE) synthesis showed a maximum at on OTR of 12?14 mmol L^?1 h^?1, while both apple juice clarifying and macerating activities gave two maxima at 14 and 60 mmol L^?1 h^?1 due to the optima of PE and endo-PG. Macerating activity showed a high value at OTR optimal for PL production as well.     

Effects of temperature on growth and metabolism in juvenile turbot

The effects of constant temperatures on growth, food efficiency, and physiological status were studied in four different batches of juvenile turbot. The growth responses were studied in three experiments lasting 70–85 days under 8–20° C thermal conditions. There was a positive correlation between growth and temperature from 8 to 17° C and a plateau was observed from 17 to 20° C. In fish fed to satiety, specific growth rate was positively correlated to the food intake, which was double at 20° C, compared with 8° C. Minor changes were observed in food efficiency. Body fat deposition decreased as temperature increased (25% lower at 20° C, compared with 8° C). Apparent food conversion, PER (protein efficiency ratio) and PUC (protein utilization coefficient) ranges were 0.8–0.9, 2.1–2.3 and 33–38% respectively. In 70–300 g fish, routine MO₂ increased (2.5–6.5 μmol O₂ h^?1 g bw^?1) with temperature up to 20° C, while larger turbot (500–600 g) appeared relatively thermo-independent, with a lower oxygen consumption (1.5 ìmol h^?1 g^?1). The average daily total ammonia nitrogen (TAN) and urea-N excretion per fish biomass was positively related to temperature. TAN was 30% lower at 8° C, compared with 20° C. Ingested nitrogen was mainly excreted under the final form of TAN, urea-N representing 26% of the total amount. A post-prandial peak in TAN and a delayed peak in urea-N nitrogen were observed. The hydromineral status [osmolarity, sodium, chloride and potassium blood plasma, gill (Na⁺-K⁺)-ATPase activity] of turbot was not affected by progressive changes in temperature during the acclimation period. Juvenile turbots show remarkable homeostatic capacities and so they have a relatively thermo-independent physiology within the range of temperature studied.     

Dark respiration of the stipe of Ecklonia cava (Laminariales, Phaeophyta) in relation to temperature

Sporophytes of Ecklonia cava Kjellman (Laminariales, Phaeophyta) with a stipe length of 22–102 cm were collected at 6–9 m depth in Nabeta Bay, Shimoda, central Japan by scuba diving in February (winter) and in August (summer) 1998. Dark respiration of the intact stipe of E. cava was measured at various water temperatures ranging from 15 to 27.5°C in winter and 15–30°C in summer in a closed system by using a dissolved oxygen meter. The stipe respiration was compared on whole stipe, length, surface area, volume, wet weight and dry weight bases. On each basis, the stipe respiration always increased with a rise in water temperature within the temperature range investigated. The stipes showed similar respiration rates on each basis of length, surface area, volume, wet weight and dry weight at each temperature, irrespective of the stipe length. The mean respiration rates in winter (at 15–27.5°C) were: length, 16.7–32.5 μL O₂ cm^?1 h^?1; surface area, 3.2–6.2 μL O₂ cm^?2 h^?1; volume, 7.6–15.0 μL O₂ cm^?3 h^?1; wet weight, 6.2–12.2 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 43.8–88.0 μL O₂ g (dry weight)^?1 h^?1. Those for summer (at 15–30°C) were: length, 17.1–32.0 μL O₂ cm^?1 h^?1; surface area, 3.6–6.8 μL O₂ cm^?2 h^?1; volume, 9.7–18.7 μL O₂ cm^?3 h^?1; wet weight, 7.6–14.6 μL O₂ g (wet weight)^?1 h^?1; and dry weight, 49.4–95.8 μL O₂ g (dry weight)^?1 h^?1. This is the first report of the intact stipe respiration of E. cava at various temperatures.     

Studies of Elodea nuttallii grown under photorespiratory conditions. I. Photosynthetic characteristics

Abstract. The photosynthetic characteristics of Elodea nuttallii grown in wastewater in continuous flow reactors in a greenhouse were investigated. The diurnal changes in dissolved inorganic carbon (DIC), dissolved oxygen (DO) and pH were monitored. Photosynthesis removed both CO₂(aq) and HCO₃^? from the reactors. A stoichiometry of 1.19:1 was observed between HCO₃^? removal during photosynthesis and OH^? production during photosynthesis, consistent with theories regarding direct bicarbonate utilization. In laboratory experiments, the light compensation points (г_PPFD) were similar (31–35μmol m^?2 s^?1) to reported values for other macrophytes; however, the light saturation level was high (1100μmol m^?2 s^?1) and similar to values reported for aerial portions Of heterophyllous macrophytes. The kinetics of photosynthetic oxygen evolution (K_m (CO₂) = 96mmol m^?3; V_max= 133mmol g^?1 Chl h^?1) and the CO₂ compensation point (г= 44cm³ m^?3) suggested an adaptive, low photorespiratory state in response to low carbon concentrations. Photosynthetic V_max values were slightly, but significantly higher (P 0.001) at pH 8.0 compared to pH 4.5. While CO₂ utilization at pH 8 could account for most of the observed phototsynthetic rates, an HCO₃^? component was present, suggesting two separate transport systems for HCO₃^? and CO₂(aq) in E. nuttallii. The activity of RUBISCO (160.3 mmol g^?1 Chl h^?1 was one of the highest reported values for aquatic macrophytes. Compared to RUBISCO, we observed lower activities of the β-carboxylating enzymes phopho enolpyruvate carboyxlase (PEPcase), 24.1 mmol g^?1 Chl h^?1; phosphor enol pyruvate carboxykinase (PEPCKase), 14 mmol g^?1 Chl h^?1. This suggests that the potential light-independent fixation of carbon in E. nuttallii was much less than RUBISCO-dependent fixation. The RUBISCO/PEPcase ratio was 6.6, indicating that E. nuttallii was similar to Myriophyllum sp. in possessing a physiological adaptation to low CO₂ levels which is hypothesized to include carbonic anhydrase (CA) and an active transport system for HCO₃^?. CA levels were surprisingly low in E. nuttallii (14.2 EUmg Chl^?).     

Effect of controlled oxygen limitation on Candida shehatae physiology for ethanol production from xylose and glucose

Carbon distribution and kinetics of Candida shehatae were studied in fed-batch fermentation with xylose or glucose (separately) as the carbon source in mineral medium. The fermentations were carried out in two phases, an aerobic phase dedicated to growth followed by an oxygen limitation phase dedicated to ethanol production. Oxygen limitation was quantified with an average specific oxygen uptake rate (OUR) varying between 0.30 and 2.48 mmolO₂ g dry cell weight (DCW)^?1 h^?1, the maximum value before the aerobic shift. The relations among respiration, growth, ethanol production and polyol production were investigated. It appeared that ethanol was produced to provide energy, and polyols (arabitol, ribitol, glycerol and xylitol) were produced to reoxidize NADH from assimilatory reactions and from the co-factor imbalance of the two-first enzymatic steps of xylose uptake. Hence, to manage carbon flux to ethanol production, oxygen limitation was a major controlled parameter; an oxygen limitation corresponding to an average specific OUR of 1.19 mmolO₂ g DCW^?1 h^?1 allowed maximization of the ethanol yield over xylose (0.327 g g^?1), the average productivity (2.2 g l^?1 h^?1) and the ethanol final titer (48.81 g l^?1). For glucose fermentation, the ethanol yield over glucose was the highest (0.411 g g^?1) when the specific OUR was low, corresponding to an average specific OUR of 0.30 mmolO₂ g DCW^?1 h^?1, whereas the average ethanol productivity and ethanol final titer reached the maximum values of 1.81 g l^?1 h^?1 and 54.19 g l^?1 when the specific OUR was the highest.     

Diversity of aerobic anoxygenic phototrophic bacteria in paddy soil and their response to elevated atmospheric CO2

Aerobic anoxygenic phototrophic bacteria (AAnPB) are recognized as an important group driving the global carbon cycling. However, the diversity of AAnPB in terrestrial environment remains largely unknown as well as their responses to the elevated atmospheric CO₂. By using culture‐independent techniques, the diversity of AAnPB in paddy soil and the changes in response to the rising atmospheric CO₂ were investigated within China FACE (Free‐air CO₂ enrichment) platform. There was a phylogenetically diverse AAnPB community with large population size residing in paddy soil. The community structure of AAnPB in bulk and rhizospheric soils stayed almost identical, while the population size was higher in rhizospheric [2.0–2.5 × 10⁸ copy number of pufM genes g^?1 dry weight soil (d.w.s.)] than that in bulk (0.7–0.8 × 10⁸ g^?1 d.w.s.) soils. Elevated atmospheric CO₂ appeared to significantly stimulate AAnPB abundance (up to 1.4–1.5 × 10⁸ g^?1 d.w.s.) and result in a higher AAnPB percentage in total bacterial community (from 0.5% up to 1.5%) in bulk soil, whereas no significant effect was observed in rhizospheric soil. Our results would extend the functional ecotypes of AAnPB and indicate that environmental changes associated with the rising atmospheric CO₂ might affect AAnPB community in paddy soil.