Production of lactic acid and byproducts from waste potato starch by <Emphasis Type="Italic">Rhizopus arrhizus</Emphasis>: role of nitrogen sources

Summary Lactic acid was produced by Rhizopus arrhizus using waste potato starch as the substrate. The aim of this study was to identify the role of nitrogen sources and their impact on the formation of lactic acid and associated byproducts. Ammonium sulphate, ammonium nitrate, urea, yeast extract and peptone were assessed in conjunction with various ratios of carbon to nitrogen (C:N). Fermentation media with a low C:N ratio enhanced the production of lactic acid, biomass and ethanol, while a high C:N ratio favoured the production of fumaric acid. Ammonium nitrate appeared to be the most suitable nitrogen source for achieving a high and stable lactic acid yield, and minimizing the production of byproducts such as biomass and ethanol, while urea proved to be the least favourable nitrogen source. Yeast extract and peptone appeared to improve fungal cell growth. The kinetics data revealed that a high concentration of ammonium nitrate enhanced the lactic acid productivity. The maximum lactic acid concentration of 36.4 g/l, representing a yield of 91%, was obtained with addition of 0.909 g/l ammonium nitrate in 32 h.     

Effect of nitrogen sources on oxidoreductive enzymes and ethanol production during D-xylose fermentation by Candida shehatae.

The effect on D-xylose utilization and the corresponding xylitol and ethanol production by Candida shehatae (ATCC 22984) were examined with different nitrogen sources. These included organic (urea, asparagine, and peptone) and inorganic (ammonium chloride, ammonium nitrate, ammonium sulphate, and potassium nitrate) sources. Candida shehatae did not grow on potassium nitrate. Improved ethanol production (Y(p/s), yield coefficient (grams product/grams substrate), 0.34) was observed when organic nitrogen sources were used. Correspondingly, the xylitol production was also higher with organic sources. Ammonium sulphate showed the highest ethanol:xylitol ratio (11.0) among all the nitrogen sources tested. The ratio of NADH- to NADPH-linked D-xylose reductase (EC 1.1.1.21) appeared to be rate limiting during ethanologenesis of D-xylose. The levels of xylitol dehydrogenase (EC 1.1.1.9) were also elevated in the presence of organic nitrogen sources. These results may be useful in the optimization of alcohol production by C. shehatae during continuous fermentation of D-xylose.     

Anaerobic nitrate reduction to ammonium in two strains isolated from coastal marine sediment: A dissimilatory pathway

Abstract: A total of 28 nitrate-reducing bacteria were isolated from marine sediment (Mediterranean coast of France) in which dissimilatory reduction of nitrate to ammonium (DRNA) was estimated as 80% of the overall nitrate consumption. Thirteen isolates were considered as denitrifiers and ten as dissimilatory ammonium producers. ¹⁵N ammonium production from ¹⁵N nitrate by an Enterobacter sp. and a Vibrio sp., the predominant bacteria involved in nitrate ammonification in marine sediment, was characterized in pure culture studies. For both strains studied, nitrate-limited culture (1 mM) produced ammonium as the main product of nitrate reduction (> 90%) while in the presence of 10 mM nitrate, nitrite was accumulated in the spent media and ammonia production was less efficient. Concomitantly with the dissimilation of nitrate to nitrite and ammonium the molar yield of growth on glucose increased. Metabolic products of glucose were investigated under different growth conditions. Under anaerobic conditions without nitrate, ethanol was formed as the main product; in the presence of nitrate, ethanol disappeared and acetate increased concomitantly with an increased amount of ammonium. These results indicate that nitrite reduction to ammonium allows NAD regeneration and ATP synthesis through acetate formation, instead of ethanol formation which was favoured in the absence of nitrate.     

白葡萄酒活性干酵母对不同氮源利用的研究

选用5种不同的白葡萄酒活性干酵母,以硫酸铵、氯化铵、硝酸铵、尿素、酵母粉等5种物质为氮源,观察其生长量并称量菌体重,以此分析其对氮源利用情况及不同氮源对酵母生长的影响。研究表明:供试菌系在不同氮源中均能生长。不同氮源对酵母的生长速度和生长量有不同影响;不同酵母菌种对不同氮源的利用也有差异。在以酵母粉为氮源的培养基中生长最好。在实验提供的氮源中,酵母粉为供试菌最优氮源,其次是硫酸铵,氯化铵与硫酸铵基本相当,而硝酸铵最差。8#菌种对各种氮源的利用能力相对较强。17#菌种对各种氮源的利用能力最弱。     

Nitrogen acquisition in four co-existing species from an upland acidic grassland

The concentration of both nitrate and ammonium nitrogen was measured in soil taken from an upland acidic (pH 4.5) grassland habitat, containing four co-existing species, Deschampsia flexuosa (L.) Trin., Festuca ovina L., Juncus squarrosus L. and Nardus stricta L. Both nitrate and ammonium nitrogen were found to be present in the soil, in similarly small quantities. The effect of both sources of nitrogen on relative growth rate was studied, and an attempt was made to determine whether nitrate or ammonium nitrogen is the immediate source of nitrogen for these plants using assays of nitrate reductase (EC 1.6.6.2) and ammonium uptake. All four species showed larger growth rates on the same concentration of ammonium nitrogen compared to nitrate nitrogen. All species showed low activities of leaf nitrate reductase, even in plants grown on 18 mol nitrate m⁻³. Ammonium uptake activity appeared to be higher in species which showed the lowest nitrate reductase activity and least response to increasing nitrate concentration in the growth medium.     

The effect of different nitrogen and carbon sources on amino acid synthesis in Ulva,Dictyota and Pterocladia

Summary This investigation includes a study of the effect of ammonium salt, nitrate and urea as nitrogen sources; vitamin B₆ as cofactor in transamination, and of acetate, pyruvate and glucose as carbon sources on the dry weight, total nitrogen and amino acid synthesis in Ulva, Dictyota and Pterocladia. The results showed that urea and to a lesser extent ammonium salt were better nitrogen sources for either Ulva or Pterocladia, while ammonium salt was best for Dictyota. Vitamin B₆ was effective in transaminations and resynthesis of amino acids in the three marine algae, especially Ulva. Pyruvate was a better carbon source than either acetate or glucose in increasing dry weights, total nitrogen and amino acid synthesis in Ulva and Dictyota, whereas acetate was best in Pterocladia.     

Growth of Esteya vermicola in media amended with nitrogen sources yields conidia with increased predacity and resistance to environmental stress

Esteya vermicola , an endoparasitic fungus of pinewood nematode, exhibits great potential as a biological agent against nematodes. In this study to enhance the sporulation, predacity, and environmental resistance of E. vermicola, various nitrogen sources, such as glycine, L-leucine, and ammonium nitrate, were tested. The supplement of glycine and L-leucine had a significant influence on the growth rate of the colony, enhancing colony dry mass by 5-fold more than did ammonium nitrate or the control. Of the nitrogen sources tested, ammonium nitrate and L-leucine promoted sporulation, yielding more than 6 × 10(6) CFU/g, while glycine enhanced the proportion of lunate spores. Meanwhile, the supplement of nitrogen sources had a significant influence on adhesive rate and mortality rate against Bursaphelenchus xylophilus . Moreover, the supplement of glycine enhanced the survival rate against heat stress by more than 3-fold that of L-leucine, ammonium nitrate, and control. The spores produced in media amended with glycine, L-leucine, and ammonium nitrate had slightly but not significantly higher UV resistance and drought resistance than spores produced without nitrogen sources. These results suggested that the addition of glycine resulted in the production of E. vermicola conidia with increased predacity and resistance to environmental stress that may be more suitable for control of pine wilt disease.     

Heterotrophic nitrification by Arthrobacter sp. (strain 9006) as influenced by different cultural conditions,growth state and acetate metabolism

An Arthrobacter sp. (strain 9006), isolated from lake water, accumulated nitrite up to about 15 mg N/l, but no nitrate. In a mineral medium supplemented with tryptone, yeast extract, acetate and ammonium, the cells released nitrite into the medium parallel to growth or when growth had virtually ceased. The nitrite formed was proportional to the initial acetate concentration, indicating an involvement of acetate metabolism with nitrification. The organism grew with a wide variety of organic carbon sources, but washed cells formed nitrite from ammonium only in the presence of citrate, malate, acetate or ethanol. Magnesium ions were required for nitrification of ammonium and could not be replaced by other divalent metal ions. Analysis of the glyoxylate cycle key enzymes in washed suspensions incubated in a minimal medium revealed that isocitrate lyase and malate synthase were most active during the nitrification phase. Nitrite accumulation but not growth was inhibited by glucose, tryptone and yeast extract. A possible explanation for the different nitrification patterns during growth is based on the regulatory properties of glyoxylate cycle enzymes.Abbreviations IL Isocitrate lyase [threo-D_s-isocitrate glyoxylate-lase, E.C. 4.1.3.1.] - MS malate synthase [l-malate glyoxylate-lyase (CoA-acetylating), E.C. 4.1.3.2.]     

Growth, nitrogen utilization and biodiesel potential for two chlorophytes grown on ammonium, nitrate or urea

Nitrogen removal from wastewater by algae provides the potential benefit of producing lipids for biodiesel and biomass for anaerobic digestion. Further, ammonium is the renewable form of nitrogen produced during anaerobic digestion and one of the main nitrogen sources associated with wastewater. The wastewater isolates Scenedesmus sp. 131 and Monoraphidium sp. 92 were grown with ammonium, nitrate, or urea in the presence of 5 % CO₂, and ammonium and nitrate in the presence of air to optimize the growth and biofuel production of these chlorophytes. Results showed that growth on ammonium, in both 5 % CO₂ and air, caused a significant decrease in pH during the exponential phase causing growth inhibition due to the low buffering capacity of the medium. Therefore, biological buffers and pH controllers were utilized to prevent a decrease in pH. Growth on ammonium with pH control (synthetic buffers or KOH dosing) demonstrated that growth (rate and yield), biodiesel production, and ammonium utilization, similar to nitrate- and urea-amended treatments, can be achieved if sufficient CO₂ is available. Since the use of buffers is economically limited to laboratory-scale experiments, chemical pH control could bridge the gap encountered in the scale-up to industrial processes.     

Influence of Carbon Source on Nitrate Removal by Nitrate-Tolerant Klebsiella oxytoca CECT 4460 in Batch and Chemostat Cultures

The nitrate-tolerant organism Klebsiella oxytoca CECT 4460 tolerates nitrate at concentrations up to 1 M and is used to treat wastewater with high nitrate loads in industrial wastewater treatment plants. We studied the influence of the C source (glycerol or sucrose or both) on the growth rate and the efficiency of nitrate removal under laboratory conditions. With sucrose as the sole C source the maximum specific growth rate was 0.3 h⁻¹, whereas with glycerol it was 0.45 h⁻¹. In batch cultures K. oxytoca cells grown on sucrose or glycerol were able to immediately use sucrose as a sole C source, suggesting that sucrose uptake and metabolism were constitutive. In contrast, glycerol uptake occurred preferentially in glycerol-grown cells. Independent of the preculture conditions, when sucrose and glycerol were added simultaneously to batch cultures, the sucrose was used first, and once the supply of sucrose was exhausted, the glycerol was consumed. Utilization of nitrate as an N source occurred without nitrite or ammonium accumulation when glycerol was used, but nitrite accumulated when sucrose was used. In chemostat cultures K. oxytoca CECT 4460 efficiently removed nitrate without accumulation of nitrate or ammonium when sucrose, glycerol, or mixtures of these two C sources were used. The growth yields and the efficiencies of C and N utilization were determined at different growth rates in chemostat cultures. Regardless of the C source, yield carbon (Y_C) ranged between 1.3 and 1.0 g (dry weight) per g of sucrose C or glycerol C consumed. Regardless of the specific growth rate and the C source, yield nitrogen (Y_N) ranged from 17.2 to 12.5 g (dry weight) per g of nitrate N consumed. In contrast to batch cultures, in continuous cultures glycerol and sucrose were utilized simultaneously, although the specific rate of sucrose consumption was higher than the specific rate of glycerol consumption. In continuous cultures double-nutrient-limited growth appeared with respect to the C/N ratio of the feed medium and the dilution rate, so that for a C/N ratio between 10 and 30 and a growth rate of 0.1 h⁻¹ the process led to simultaneous and efficient removal of the C and N sources used. At a growth rate of 0.2 h⁻¹ the zone of double limitation was between 8 and 11. This suggests that the regimen of double limitation is influenced by the C/N ratio and the growth rate. The results of these experiments were validated by pulse assays.     

Comparative proteomic analysis reveals insights into anoxic growth of Methyloversatilis universalis FAM5 on methanol and ethanol

Methyloversatilis universalis FAM5 is a facultative methylotrophic bacterium that has been found in a variety of natural and engineered ecosystems. The goal of this study was to investigate M. universalis FAM5 responses to different electron/carbon donors, e.g. methanol or ethanol, during anoxic growth in chemostats with nitrate as the electron acceptor. During steady‐state anoxic growth on either methanol or ethanol, over 90% of the influent nitrate was reduced primarily to nitrite. The cell yield on methanol was lower, possibly due to high energy requirements for C₁ assimilation. Label‐free proteomics further revealed that methanol‐grown cells displayed elevated concentrations of the enzymes involved in C₁ metabolism (H₄MPT/H₄F pathways, formate oxidation and serine cycle). In contrast, C₂ metabolism (glyoxylate shunt and tri‐carboxylic acid cycle) and polyhydroxy‐β‐butyrate (PHB) synthesis related proteins were overrepresented during subsequent growth on ethanol. Notably, the expression of respiratory nitrate reductase was not affected by the carbon sources applied. Furthermore, the changes in the proteome upon switching back to methanol were mostly reversible. Therefore, M. universalis displays wide‐ranging responses to adapt between growth on methanol and ethanol. Such metabolic versatility could be particularly useful in wastewater treatment systems, which need to switch between different electron donors, while still reliably meeting effluent nitrogen discharge goals.     

Effect of nutritional conditions on dye removal from textile effluent by <Emphasis Type="Italic">Aspergillus lentulus</Emphasis>

The nutritional conditions supporting growth and maximum dye removal by Aspergillus lentulus have been investigated. Initially a composite media containing yeast extract, glucose and mineral components was used and the effect of various components on dye removal was studied. For maximum dye removal (≈100%), ≥0.5% (w/v) glucose and ≥0.25% (w/v) yeast extract were essential. While glucose played an important role in pellet formation, which in turn was important for dye removal, yeast extract contributed towards higher biomass production. Mineral components (except NH₄NO₃) did not affect dye removal significantly. Next the alternate sources of carbon (molasses, jaggery, starch and sodium acetate) and nitrogen (peptone, urea, ammonium nitrate, sodium nitrate and ammonium chloride) were tested. Among carbon sources, all the sources produced almost complete dye removal in 48 h (more than 97% in 24 h), except sodium acetate (64% in 48 h). All the tested nitrogen sources resulted in >90% dye removal in 48 h. Yeast extract and peptone gave best results with high dye removal rate (9.8 and 8.1 mg/l/h, respectively). However, among the low cost alternates, urea and NH₄Cl came out to be suitable sources due to the high uptake capacity of the biomass produced coupled with high dye removal rate in case of NH₄Cl. Therefore, a combination of urea and NH₄Cl was tested, which produced complete dye removal with a high dye removal rate (10 mg/l/h). Finally the modified composite media containing urea and NH₄Cl as nitrogen sources and glucose as carbon source was utilized for effluent treatment. Results indicated that performance of modified composite media was at par with composite media for supporting growth of A. lentulus and dye removal from the textile effluent.     

A comparison of carbon/energy and complex nitrogen sources for bacterial sulphate-reduction: potential applications to bioprecipitation of toxic metals as sulphides

Detailed nutrient requirements were determined to maximise efficacy of a sulphate-reducing bacterial mixed culture for biotechnological removal of sulphate, acidity and toxic metals from waste waters. In batch culture, lactate produced the greatest biomass, while ethanol was more effective in stimulating sulphide production and acetate was less effective. The presence of additional bicarbonate and H₂ only marginally stimulated sulphide production. The sulphide output per unit of biomass was greatest using ethanol as substrate. In continuous culture, ethanol and lactate were used directly as efficient substrates for sulphate reduction while acetate yielded only slow growth. Glucose was utilised following fermentation to organic acids and therefore had a deleterious effect on pH. Ethanol was selected as the most efficient substrate due to cost and efficient yield of sulphide. On ethanol, the presence of additional carbon sources had no effect on growth or sulphate reduction in batch culture but the presence of complex nitrogen sources (yeast extract or cornsteep) stimulated both. Cornsteep showed the strongest effect and was also preferred on cost grounds. In continuous culture, cornsteep significantly improved the yield of sulphate reduced per unit of ethanol consumed. These results suggest that the most efficient nutrient regime for bioremediation using sulphate-reducing bacteria required both ethanol as carbon source and cornsteep as a complex nitrogen source.     

Engineering of the redox imbalance of Fusarium oxysporum enables anaerobic growth on xylose

Dissimilatory nitrate reduction metabolism, of the natural xylose-fermenting fungus Fusarium oxysporum, was used as a strategy to achieve anaerobic growth and ethanol production from xylose. Beneficial alterations of the redox fluxes and thereby of the xylose metabolism were obtained by taking advantage of the regeneration of the cofactor NAD(+) during the denitrification process. In batch cultivations, nitrate sustained growth under anaerobic conditions (1.21 g L(-1) biomass) and simultaneously a maximum yield of 0.55 moles of ethanol per mole of xylose was achieved, whereas substitution of nitrate with ammonium limited the growth significantly (0.15 g L(-1) biomass). Using nitrate, the maximum acetate yield was 0.21 moles per mole of xylose and no xylitol excretion was observed. Furthermore, the network structure in the central carbon metabolism of F. oxysporum was characterized in steady state. F. oxysporum grew anaerobically on [1-(13)C] labelled glucose and unlabelled xylose in chemostat cultivation with nitrate as nitrogen source. The use of labelled substrate allowed the precise determination of the glucose and xylose contribution to the carbon fluxes in the central metabolism of this poorly described microorganism. It was demonstrated that dissimilatory nitrate reduction allows F. oxysporum to exhibit typical respiratory metabolic behaviour with a highly active TCA cycle and a large demand for NADPH.     

Differential Effects of Ammonium and Nitrate on Growth Performance of <i>Glechoma longituba</i> under Heterogeneous Cd Stress

Water, minerals, nutrients, etc., can be shared by physiological integration among inter-connected ramets of clonal plants. Nitrogen plays an important role in alleviating cadmium (Cd) stress for clonal plants. But how different forms of nitrogen affect growth performance of clonal plants subjected to heterogeneous Cd stress still remains poorly understood. A pot experiment was conducted to investigate the differential effects of ammonium and nitrate on growth performance of Glechoma longituba under heterogeneous Cd stress. In the experiment, parent ramets of Glechoma longituba clonal fragments were respectively supplied with modified Hoagland solution containing 7.5 mM ammonium, 7.5 mM nitrate or the same volume of nutrient solution without nitrogen. Cd solution with different concentrations (0, 0.1 or 2.0 mM) was applied to offspring ramets of the clonal fragments. Compared with control (N-free), nitrogen addition to parent ramets, especially ammonium, significantly improved antioxidant capacity [glutathione (GSH), proline (Pro), peroxidase (POD,) superoxide dismutase (SOD) and catalase (CAT)], PSII activity [maximum quantum yield of PSII (F_v/F_m) and effective quantum yield of PSII (ΦPSII)], chlorophyll content and biomass accumulation of the offspring ramets suffering from Cd stress. In addition, negative effects of nitrate on growth performance of whole clonal fragments were observed under Cd stress with high concentration (2.0 mM). Transportation or sharing of nitrogen, especially ammonium, can improve growth performance of clonal plants under heterogeneous Cd stress. The experiment provides insight into transmission mechanism of nitrogen among ramets of clonal plants suffering from heterogeneous nutrient supply. Physiological integration might be an important ecological strategy for clonal plants adapting to heterogeneous environment stress conditions.     

Laboratory metabolic evolution improves acetate tolerance and growth on acetate of ethanologenic Escherichia coli under non-aerated conditions in glucose-mineral medium

In this work, Escherichia coli MG1655 was engineered to produce ethanol and evolved in a laboratory process to obtain an acetate tolerant strain called MS04 (E. coli MG1655: ΔpflB, ΔadhE, ΔfrdA, ΔxylFGH, ΔldhA, PpflB::pdc _Zm -adhB _Zm , evolved). The growth and ethanol production kinetics of strain MS04 were determined in mineral medium, mainly under non-aerated conditions, supplemented with glucose in the presence of different concentrations of sodium acetate at pH?7.0 and at different values of acid pH and a constant concentration of sodium acetate (2?g/l). Results revealed an increase in the specific growth rate, cell mass formation, and ethanol volumetric productivity at moderate concentrations of sodium acetate (2–10?g/l), in addition to a high tolerance to acetate because it was able to grow and produce a high yield of ethanol in the presence of up to 40?g/l of sodium acetate. Genomic analysis of the ΔpflB evolved strain identified that a chromosomal deletion of 27.3?kb generates the improved growth and acetate tolerance in MG1655 ΔpflB derivative strains. This deletion comprises genes related to the respiration of nitrate, repair of alkylated DNA and synthesis of the ompC gene coding for porin C, cytochromes C, thiamine, and colonic acid. Strain MS04 is advantageous for the production of ethanol from hemicellulosic hydrolysates that contain acetate.     

Poly-3-hydroxybutyrate production byAzotobacter chroococcum

Thirty-seven soil isolates and mutants ofAzotobacter chroococcum tested for poly-3-hydroxybutyrate (PHB) production using Sudan black B staining method were found to be positive. One mutant showed a higher number of PHB-producing cells and maximum number of granules per cell. Using 2% glucose and 15 mmol/L ammonium acetate, PHB production was found to be maximum at 36 and 48 h of growth under submerged cultivation and under stationary cultivation, respectively. PHB production was found to be higher on sucrose and commercial sugar (as carbon sources) as compared to glucose and mannitol. As commercial sugar is cheaper than sucrose it was selected as carbon source for PHB production, that being found to be maximum at 1% concentration. Inorganic nitrogen sources seemed to have no stimulatory effect on the production of PHB. However, ammonium acetate (15 mmol/L) was found to be best for PHB production. Peptone (0.2 %) gave a better yield of PHB under both growth conditions. Using all optimized conditions, PHB production was studied in ten selected strains. Two of them were found to be best PHB producers under both growth conditions, one producing 621 and 740 μg/g dry mass under submerged cultivation and under stationary cultivation, respectively, while the second one produced 589 and 733 μg/g.     

Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

Different sources of nitrogen pose diverse effects to algal community, but the mechanism of inhibitory effects of nitrogen sources on freshwater diatoms is not fully understood. The purpose of this study was to compare biomass, photosynthetic activity, and morphological structure of three common freshwater diatoms (Cyclotella meneghiniana, Nitzschia sp., and Gomphonema parvulum) under different nitrogen sources (NO₃ ^? or NH₄ ⁺). The sorption characteristic of each diatom was investigated, and chlorophyll a (Chl-a) content and oxygen evolution rate were analyzed to investigate stress of different nitrogen sources on each diatom in the batch experiments. Ammonium lowered the growth rate of C. meneghiniana and Nitzschia sp. when it was supplied in addition to growth-saturating nitrate concentrations, suggesting a combined effect of inhibition of nitrate uptake and direct ammonium stress. Oxygen evolution rate of Nitzschia sp. showed that the direct ammonium stress on the photosynthetic activity can be alleviated by coexistence of nitrate in the nitrogen enriched treatment, but not for C. meneghiniana and G. parvulum, which may be caused by a different nitrate transporter system within algal cells. Transmission electron microscopy was used to assess the toxicity of ammonium on ultrastructural chloroplast of each diatom. Ultrastructural changes in chloroplasts showed undefined electron-dense granules and lipid droplets, but the membrane integrity of cell was maintained, suggesting an adaptation to adjustment to ammonia stress. Results showed that Cyclotella meneghiniana and Nitzschia sp. were more sensitive to ammonium stress than Gomphonema parvulum on growth, but the mechanism remains unclear.     

Different nitrogen sources and growth responses of Spirulina platensis in microenvironments

Spirulina platensis was cultivated, in comparative studies, using several sources of nitrogen. The standard source used (sodium nitrate) was the same as that used in the synthetic medium Zarrouk, whereas the alternative nitrogen sources consisted of ammonium nitrate, urea, ammonium chloride, ammonium sulphate or acid ammonium phosphate. The initial nitrogen concentrations tested were 0.01, 0.03 and 0.05 M in an aerated photobioreactor at 30 °C, with an illuminance of 1900 lux, and 12 h-light/12 h-dark photoperiod over a period of 672 h. Maximum biomass was produced in medium containing sodium nitrate (0.01–0.03–0.05 M), followed by ammonium nitrate (0.01 M) and urea (0.01 M). The final biomass concentrations were 1.992 g l^–1 (0.03 M sodium nitrate), 1.628 g l^–1 (0.05 M sodium nitrate), 1.559 g l^–1 (0.01 M sodium nitrate), 0.993 g l^–1 (0.01 M ammonium nitrate) and 0.910 g l^–1 (0.01 M urea). This suggested that it is possible to utilize nitrogen sources other than sodium nitrate for growing S. platensis, in order to decrease the production costs of scaled up projects.     

Production of l-glutamic acid by aBacillus sP

A strain ofBacillus cereus var.mycoides isolated from Burdwan soil producesl-glutamate in the medium. The strain is able to grow and produce in a synthetic medium but supplementation with casamino acid or yeast extract improves the yield. Maintenance of pH of the fermentation medium near neutrality prolongs the active growth period and improves the yield. Glucose and ammonium nitrate were found to be most suitable carbon and nitrogen sources, respectively. Cane sugar molasses (as a substitute for glucose) significantly stimulated the growth but glutamate production was less. Various B vitamins stimulate the growth and glutamate yield. The yield of glutamate under optimal condition is 5.2 g/l.