Bifurcations in a white-blood-cell production model

We study the dynamics of a model of white-blood-cell (WBC) production. The model consists of two compartmental differential equations with two discrete delays. We show that from normal to pathological parameter values, the system undergoes supercritical Hopf bifurcations and saddle-node bifurcations of limit cycles. We characterize the steady states of the system and perform a bifurcation analysis. Our results indicate that an increase in apoptosis rate of either hematopoietic stem cells or WBC precursors induces a Hopf bifurcation and an oscillatory regime takes place. These oscillations are seen in some hematological diseases.     

Biodiesel production using a membrane reactor

The immiscibility of canola oil in methanol provides a mass-transfer challenge in the early stages of the transesterification of canola oil in the production of fatty acid methyl esters (FAME or biodiesel). To overcome or rather, exploit this situation, a two-phase membrane reactor was developed to produce FAME from canola oil and methanol. The transesterification of canola oil was performed via both acid- or base-catalysis. Runs were performed in the membrane reactor in semi-batch mode at 60, 65 and 70 degrees C and at different catalyst concentrations and feed flow rates. Increases in temperature, catalyst concentration and feedstock (methanol/oil) flow rate significantly increased the conversion of oil to biodiesel. The novel reactor enabled the separation of reaction products (FAME/glycerol in methanol) from the original canola oil feed. The two-phase membrane reactor was particularly useful in removing unreacted canola oil from the FAME product yielding high purity biodiesel and shifting the reaction equilibrium to the product side.     

Acid production byRhizobium a unifying concept

Summary A study was made of the acid-producing characteristics of 717 strains of Rhizobium in relation to the taxonomic position of the host legume. The hypothesis advanced is that the slow-growing non acid-producing type of Rhizobium commonly associated with tropical legumes represents the ancient form of the symbiont which has persisted unchanged because acid production during growth in the rhizosphere in acid soils would react unfavourably against survival. When the host legume becomes adapted to non-acid soils this restriction is lifted from the Rhizobium. The faster growth rate that is possible with an acid-producing metabolism and the competitive advantage this confers in the rhizosphere then ensures that the Rhizobium strains in effective symbiosis with the host become acid producers. If a group of legumes is found to be characteristically associated with Rhizobium that is strongly acid-producing it is an indication that the host group is an advanced one that has become strongly adapted to non-acid soils.The significance of this hypothesis to agronomic practice and to the taxonomy of legumes and of Rhizobium is discussed.     

Biological hydrogen production using a membrane bioreactor

A cross-flow membrane was coupled to a chemostat to create an anaerobic membrane bioreactor (MBR) for biological hydrogen production. The reactor was fed glucose (10,000 mg/L) and inoculated with a soil inoculum heat-treated to kill non-spore-forming methanogens. Hydrogen gas was consistently produced at a concentration of 57-60% in the headspace under all conditions. When operated in chemostat mode (no flow through the membrane) at a hydraulic retention time (HRT) of 3.3 h, 90% of the glucose was removed, producing 2200 mg/L of cells and 500 mL/h of biogas. When operated in MBR mode, the solids retention time (SRT) was increased to SRT = 12 h producing a solids concentration in the reactor of 5800 mg/L. This SRT increased the overall glucose utilization (98%), the biogas production rate (640 mL/h), and the conversion efficiency of glucose-to-hydrogen from 22% (no MBR) to 25% (based on a maximum of 4 mol-H(2)/mol-glucose). When the SRT was increased from 5 h to 48 h, glucose utilization (99%) and biomass concentrations (8,800 +/- 600 mg/L) both increased. However, the biogas production decreased (310 +/- 40 mL/h) and the glucose-to-hydrogen conversion efficiency decreased from 37 +/- 4% to 18 +/- 3%. Sustained permeate flows through the membrane were in the range of 57 to 60 L/m(2) h for three different membrane pore sizes (0.3, 0.5, and 0.8 microm). Most (93.7% to 99.3%) of the membrane resistance was due to internal fouling and the reversible cake resistance, and not the membrane itself. Regular backpulsing was essential for maintaining permeate flux through the membrane. Analysis of DNA sequences using ribosomal intergenic spacer analysis indicated bacteria were most closely related to members of Clostridiaceae and Flexibacteraceae, including Clostridium acidisoli CAC237756 (97%), Linmingia china AF481148 (97%), and Cytophaga sp. MDA2507 AF238333 (99%). No PCR amplification of 16s rRNA genes was obtained when archaea-specific primers were used.     

Antibiotic production in a spatially structured environment

Ecological factors influencing the effects of antibiotic production were explored experimentally and theoretically. A spatially structured model was used to model the dynamics of antibiotic-producing and nonproducing bacteria in which growth of the nonproducers was reduced by neighbouring antibiotic producers. Various factors affecting spatial interactions between the bacteria were examined for their impact on antibiotic producers. Spatial clustering had a positive impact on the effect of antibiotic production, as measured by the decline in growth of the nonproducing strain, while increasing the initial density of the nonproducing strain had a negative impact. Experiments examined the growth of antibiotic-producing Streptomyces species and a nonproducing, antibiotic-sensitive strain of Bacillus subtilis that were coinoculated on surface media. There was an effect of the Streptomyces on Bacillus growth in some experiments but not in others. In light of the predictions from the model, unintentional clustering of cells is a more likely explanation for this finding than different initial Bacillus densities. The importance of spatial structure seen in this study is consistent with a terrestrial rather than an aquatic distribution of antibiotic-producing bacteria, and may have implications in the search for novel antibiotics.     

Cytokine production by a megakaryocytic cell line

Summary The regulation of megakaryopoeisis by cytokines is not yet well understood. It is possible that autocrine loops are established during megakaryocyte growth and differentiation, aiding in the maturation of these cells. The CHRF-288-11 human megakaryoblastic cell line has been examined for cytokine production in growing cells and cells stimulated to differentiate by the addition of phorbol esters. It has been demonstrated that these cells produce RNA corresponding to the interleukins IL-1α, 1β, 3, 7, 8, and 11, granulocyte-macrophage colony stimulating factor (GM-CSF), stem cell factor (SCF), transforming growth factor-β (TGF-β), tumor necrosis factor-α (TNF-α), interferon-α (INF-α), and basic fibroblast growth factor (bFGF). Additionaly, RNA corresponding to the receptors for IL-6, GM-CSF, SCF, INF-α,β, bFGF, and monocyte colony stimulating factor (M-CSF) were also expressed by the cells. The receptor for TNF-α was detected immunologically. Analysis at the protein level demonstrated that significant amounts of INF-α, TNF-α, GM-CSF, SCF, IL-1α, and a soluble form of the IL-6 receptor were produced by the cells. Addition of phorbol esters to CHRF-288-11 cells enhances their megakaryocytic phenotype; such treatment also results in increased secretion of INF-α, TNF-α, and GM-CSF. These results suggest that potential autocrine loops are established during the differentiation of CHRF-288-11 cells, which may alter the capability of the cell to differentiate. These findings are similar to those recently obtained for marrow-derived megakaryocytes (Jiang et al.) suggesting that CHRF-288-11 cells provide a useful model system for the study of cytokine release during megakaryocyte differentiation.     

微生物发酵法生产S-腺苷甲硫氨酸的研究进展

S-腺苷甲硫氨酸(S-adenosyl-l-methionine, SAM)广泛存在于生物体内,主要参与生物体内的转甲基过程、转硫过程及转氨丙基过程,具有重要的生理功能,其生产备受重视。目前SAM生产的研究主要集中于微生物发酵法,该方法与化学合成法和酶催化法相比,成本较低且更容易实现工业化生产。随着需求量的迅速增加,通过菌种改良提高SAM产量备受关注。当前SAM生产菌种改良的主要策略包括常规育种和代谢工程。本文综述了提高微生物生产SAM能力的近期研究进展并探讨了SAM生产中的瓶颈问题及解决方法,以期为进一步提高SAM产量提供思路。     

Engineering a beta-carotene ketolase for astaxanthin production

A new beta-carotene ketolase gene (crtW) was cloned from an environmental isolate Sphingomonas sp. DC18. A robust and reliable color screen was developed for protein engineering to improve its activity on hydroxylated carotenoids for astaxanthin production. Localized random mutagenesis was performed on the crtW gene including the upstream ribosomal binding site (RBS). Six mutations (H96L, R203W, A205V, A208V, F213L and A215T) in the crtW gene were isolated multiple times that showed improved astaxanthin production. These mutations were localized near the conserved histidine motifs, which were proposed for binding iron required for enzymatic activity. Combination of two of the mutations (R203W/F213L) further improved astaxanthin production. One mutation at the RBS (a438t) was shown to have additional effect on improving astaxanthin production. Most of the mutants still retained high activity on beta-carotene, however, the F213L single mutant and the R203W/F213L double mutant that yielded the highest improvement for astaxanthin production showed decreased activity for canthaxanthin production.     

Carotenoid production by Xanthophyllomyces dendrorhous: use of pineapple juice as a production medium

Aims:  To select a carotenoid-hyperproducing mutant and to formulate pineapple juice as a carotenoid production medium.
Methods and Results:  Yeast strain of Xanthophyllomyces dendrorhous mutant GM 807 (derived from gamma irradiation) and the mutant n78 (from neutron irradiation) were selected based on higher carotenoid production in diluted pineapple juice as a medium. The selected strain was evaluated under various concentrations of pineapple juice. The results obtained in the study demonstrate that the mutant GM 807 enhanced production by 65·8% when using pineapple juice as medium at 10% dilution in place of yeast malt medium.
Conclusion:  Pineapple juice could be used as a sole medium for carotenoid production.
Significance and Impact of the Study:  Our results provide useful information for the design of production media for carotenoids to be used in various applications.     

Net primary production and net ecosystem production of a boreal black spruce wildfire chronosequence

Net primary production (NPP) was measured in seven black spruce (Picea mariana (Mill.) BSP)‐dominated sites comprising a boreal forest chronosequence near Thompson, Man., Canada. The sites burned between 1998 and 1850, and each contained separate well‐ and poorly drained stands. All components of NPP were measured, most for 3 consecutive years. Total NPP was low (50–100 g C m^?2 yr^?1) immediately after fire, highest 12–20 years after fire (332 and 521 g C m^?2 yr^?1 in the dry and wet stands, respectively) but 50% lower than this in the oldest stands. Tree NPP was highest 37 years after fire but 16–39% lower in older stands, and was dominated by deciduous seedlings in the young stands and by black spruce trees (>85%) in the older stands. The chronosequence was unreplicated but these results were consistent with 14 secondary sites sampled across the landscape. Bryophytes comprised a large percentage of aboveground NPP in the poorly drained stands, while belowground NPP was 0–40% of total NPP. Interannual NPP variability was greater in the youngest stands, the poorly drained stands, and for understory and detritus production. Net ecosystem production (NEP), calculated using heterotrophic soil and woody debris respiration data from previous studies in this chronosequence, implied that the youngest stands were moderate C sources (roughly, 100 g C m^?2 yr^?1), the middle‐aged stands relatively strong sinks (100–300 g C m^?2 yr^?1), and the oldest stands about neutral with respect to the atmosphere. The ecosystem approach employed in this study provided realistic estimates of chronosequence NPP and NEP, demonstrated the profound impact of wildfire on forest–atmosphere C exchange, and emphasized the need to account for soil drainage, bryophyte production, and species succession when modeling boreal forest C fluxes.     

Protamylasse, a residual compound of industrial starch production, provides a suitable medium for large-scale cyanophycin production

Protamylasse is a residual compound occurring during the industrial production of starch from potatoes. It contains a variety of nutrients and all necessary minerals and could be used as a carbon, nitrogen, and energy source for the growth of bacteria and also for cyanophycin (CGP) biosynthesis. Media containing protamylasse as the sole compound diluted only in water were therefore examined for their suitability in CGP production. Among various bacterial strains investigated in this study, a recombinant strain of Escherichia coli DH1 harboring plasmid pMa/c5-914::cphA6803, which carries the cyanophycin synthetase structural gene (cphA) from Synechocystis sp. strain PCC6803, was found to be most suitable. Various cultivation conditions for high CGP contents were first optimized in shake flask cultures. The optimized conditions were then successfully applied to 30- and 500-liter fermentation scales in stirred tank reactors. A maximum CGP content of 28% (wt/wt) CGP per cell dry matter was obtained in 6% (vol/vol) protamylasse medium at an initial pH of 7.0 within a cultivation period of only 24 h. The CGP contents obtained with this recombinant strain employing protamylasse medium were higher than those obtained with the same strain cultivated in mineral salts medium or in expensive commercial complex media such as Luria-Bertani or Terrific broth. It was shown that most amino acids present in the protamylasse medium were almost completely utilized by the cells during cultivation. Exceptions were alanine, tryptophan, tyrosine, and most interestingly, arginine. Furthermore, CGP was easily isolated from protamylasse-grown cells by applying the acid extraction method. The CGP exhibited a molecular mass of about 26 to 30 kDa and was composed of 50% (mol/mol) aspartate, 46% (mol/mol) arginine, and 4% (mol/mol) lysine. The use of cheap residual protamylasse could contribute in establishing an economically and also ecologically feasible process for the biotechnological production of CGP.     

Sago production in a New Guinea economy

The techniques used by the Sanio-Hiowe of Papua New Guinea to produce edible starch from the sago palm (Metroxylon sp.) are described. Input-output analysis demonstrates that this is a highly productive subsistence technology; nevertheless, the Sanio-Hiowe economy is characterized by an absence of intensification. This is ascribed to functional consequences of dependence on hunting and gathering in the interior. In coastal and riverine habitats, other societies using sago supplemented by fishing or horticulture can more fully exploit the potential of sago as a basis for economic intensification and a more sedentary life.This field research among the Sanio-Hiowe of Yareno hamlet was carried out from March 1966 to August 1967 with the assistance of W. Townsend and the support of a National Science Foundation dissertation research grant and a United States Public Health Service Fellowship. In earlier publicationsHiowe was spelledHeve. I have altered the spelling of Sanio words to conform to the phonemic analysis of Lewis and Lewis (1970).     

Natural flavours production: a biotechnological approach

In a growing world market for flavours, and one in which there is a distinct trend towards ‘natural’ compounds, the production of flavours via biotechnological processes offers a number of advantages. This review discusses how consumer choice, regulatory definitions and technical advances are combining to present opportunities for the commercial exploitation of biological technology for flavour production.     

Degeneration of a production strain ofstreptomyces erythreus

Коммуникации занимается дегенерации производства штамма Streptomyces erythreus. Новые Jare представлены выводы:

1. (1)
   Штамма включает в себя как sporogenous и asporogenous морфологических компонент, каждая из которых может быть делится на подтипы далее. По оценке производственной деятельности индивидуального морфологические подтипов было показано что sporogenous компонент культуры включает в себя лиц, в то время производственного asporogenous компонент включает в себя только непроизводственной или с низким уровнем производственного лиц. Микроскопического изучения показали, что sporogenous подтипов формируется прямо вегетативной hyphae, в то время как asporogenous подтипов формируется толще и сморщенное вегетативной hyphae.     
   
   

Proteinase production by a species of Cephalosporium

An unidentified Cephalosporium species produced an extracellular proteinase when grown in a variety of fermentation media under submerged culture conditions. Maximal enzyme yields were obtained in a medium containing 2% corn meal, 1% soybean meal, and 0.5% CaCO₃ in tap water. Optimal proteinase production in this medium occurred within a 72- to 96-hr growth period. High enzyme yields were also attained with media in which cottonseed meal, Fermatein, Pharmamedia, or soybean-α-protein was substituted for the soybean meal. The substitution of these ingredients for the corn meal resulted in significantly decreased proteinase yields. The addition of minerals or vitamins to the corn meal-soybean meal fermentation medium failed to enhance proteinase production. The enzyme was most active in an alkaline environment; maximal caseinolysis occurred at pH 7.5, whereas pH 8.5 was optimal for either hemoglobin or β-lactoglobulin hydrolysis. Enzymatic activity was also noted with either bovine albumin fraction V or soybean-α-protein substrates, whereas ovalbumin was not susceptible to enzymatic attack. The enzyme was stable within the pH range of 3.0 to 9.5 at 25 C for 2 hr, and at 5 C for 24 hr. The proteinase was stable upon heating for 10 min at 35 to 45 C, but it was totally inactivated at 70 C. The proteinase was unaffected by soybean inhibitor, partially inactivated by lima bean inhibitor, and completely inactivated by ovomucoid inhibitor.     

Optimization of a Bifidobacterium longum production process

Bifidobacteria are used as probiotics mainly in the dairy industry as cell suspensions or as freeze-dried additives. So far there have been no reports on a thorough investigation on factors influencing the production process or a statistical approach to the optimization thereof. A 2(8-4) fractional factorial design was used in determining the critical parameters influencing bioreactor cultivations of Bifidobacterium longum ATCC 15707. Glucose, yeast extract and l-cysteine concentrations were found critical for the cultivation of this strain. Glucose and yeast extract concentrations were further studied together with temperature in a three factor central composite design. The optimized cultivation conditions were temperature 40 degrees C, yeast extract concentration 35 gl(-1) and glucose concentration 20 gl(-1). Freeze-drying of frozen cell suspensions of B. longum was studied first in controlled temperatures and thereafter with temperature programming experiments. The results were statistically evaluated. A temperature program with a 2 h temperature gradient from -10 to 0 degrees C, a 10 h temperature gradient from 0 to +10 degrees C and a 12 h temperature hold at +10 degrees C was found best for the freeze-drying process. Temperature programming reduced drying times by over 50% and improved the product activity by over 160%.