Production of l-phenylalanine by double auxotrophic mutants of arthrobacter globiformis: Optimization of c and n-source

A number of tryptophan plus tyrosine double auxotrophic mutants isolated by NTG treatment of a glutamic acid prodcing strain of A. globiformis were found to excrete phenylalanine alone in glucose, ammonium chloride, mineral salt medium. Among 24 different carbon sources tested glucose was found to be the best and optimum for -phenylalanine production was at 350 mM level. Among 14 different inorganic and organic nitrogen sources tested ammonium chloride was the best and was optimal at 60 mM level for phenylalanine production. On the optimum level of C and N sources a yield of 1.5 g/l phenylalanine was achieved.     

A note on the effect of nitrogen source on growth of and solvent production by Clostridium acetobutylicum

A number of mono- and dicarboxylic acid amino acids, amides and inorganic ammonium sources were tested to determine their effect on the growth of and solvent production by Clostridium acetobutylicum ATCC 824. Optimum cell growth (A₆₅₀= 0.96) and solvent production (total solvents = 10.85 g/l) were obtained with the medium containing glutamic acid as the ammonium source. Similar results were obtained through three successive serial subcultures although changes in the fermentation were noted with the third subculture. Cell growth and solvent production fell after the second subculture when ammonium acetate was used as the ammonium source. Adaptation was shown to occur in a medium which contained asparagine.     

Energetics and product formation by Saccharomyces cerevisiae grown in anaerobic chemostats under nitrogen limitation

Anaerobic fermentation of glucose (20 g/l) by Saccharomyces cerevisiae CBS 8066 was studied in a chemostat (dilution rate = 0.05–0.25 h^–1) at different concentrations of the nitrogen source (5.00 g/l or 0.36 g/l ammonium sulphate). The ethanol yield (g ethanol produced/g glucose consumed) was found to be higher and the glycerol yield (g glycerol formed/g glucose consumed) lower during nitrogen limitation than under carbon limitation. The biomass yield on ATP (g dry weight biomass produced/mol ATP consumed) was consequently found to be lower during nitrogen-limited conditions.     

Direct fermentation of gelatinized sago starch to acetone–butanol–ethanol by Clostridium acetobutylicum

Direct fermentation of gelatinized sago starch into solvent (acetone–butanol–ethanol) by Clostridium acetobutylicum P262 was studied using a 250 ml Schott bottle anaerobic fermentation system. Total solvent production from fermentation using 30 g sago starch/l (11.03g/l) was comparable to fermentation using corn starch and about 2-fold higher than fermentation using potato or tapioca starch. At the range of sago starch concentration investigated (10–80 g/l), the highest total solvent production (18.82 g/l) was obtained at 50 g/l. The use of a mixture of organic and inorganic nitrogen source (yeast extract + NH₄NO₃) enhanced growth of C. acetobutylicum, starch hydrolysis and solvent production (24.47 g/l) compared to the use of yeast extract alone. This gave the yield based on sugar consumed of 0.45 g/g. Result from this study also showed that the individual concentrations of nitrogen and carbon influenced solvent production to a greater extent than did carbon to nitrogen (C/N) ratio.     

氮源对L-苏氨酸发酵的影响

以L-苏氨酸生产菌TRFC为供试菌株,研究了氮源对L-苏氨酸发酵的产量和糖酸转化率的影响。首先通过摇瓶实验确定发酵的最佳无机氮源和有机氮源分别为硫酸铵和酵母粉,进一步利用10L罐补料分批发酵确定硫酸铵和酵母粉的最佳用量,继续优化培养条件,采用发酵中后期流加硫酸铵和糖氨混合补料等措施,L-苏氨酸产量得到进一步的提高。在最优发酵条件下,通过10L罐补料分批发酵36h,产酸可达118.9g/L,糖酸转化率为47.6%。     

Study of fermentation behavior and formulation of a semidefined nutrient medium based on acid-production measurements in Z. mobilis cultures

Batch fermentations of glucose to ethanol by Z. Mobilis.(ATCC 10988) were examined in several semidefined nutrient media. The measurement of acid produced by the microorganism was used to study its transient fermentation characteristics. Limitation of nitrogen source in the semidefined medium of Rogers and coworkers(2) was found to limit the growth of this microorganism in the late stages of batch fermentations, when the initial glucose concentration was 75 g/L and higher. The microorganism exhibits a preference for inorganic nitrogen over preformed organic nitrogen provided by yeast extract. The microbial growth occurs exponentially in the presence of ammonium sulfate and yeast extract. However, in the absence of ammonium sulfate, the growth occurs in a linear fashion. The "linear" growth phase is characterized by poor cell-mass yields, and during this phase, growth and ethanol production are decoupled. An improved semi-defined growth medium is established which supports better growth rate and cellular yield, without affecting the ethanol yield.     

铁尾矿区油松根际溶磷泛菌D2的筛选鉴定及溶磷特性

从河北省迁安市马兰庄镇铁尾矿植被恢复区油松根际分离出2株溶磷细菌,经过平板初筛和摇瓶复筛得到1株溶磷能力较强的菌株D2.通过菌落形态、生理生化特性及16S rDNA序列分析,确定此菌株D2属于泛菌属.利用液体发酵试验测定不同碳源、氮源对菌株D2溶磷能力的影响,通过高效液相色谱测定D2在不同氮源条件下产生有机酸的种类和浓度.结果表明:菌株D2对磷酸三钙有较强的溶磷能力,培养液有效磷含量最高为392.13 mg·L^-1,菌株D2的溶磷能力在碳源为葡萄糖、氮源为硫酸铵时效果最好;高效液相色谱测定发现,不同氮源条件下,D2分泌有机酸的种类和浓度存在差异,以硫酸铵、氯化铵、硝酸钾、硝酸钠、硝酸铵为氮源,均产生草酸、甲酸、乙酸和柠檬酸,以硫酸铵、氯化铵、硝酸铵为氮源还产生苹果酸.相关性分析表明,乙酸含量与有效磷含量间呈显著正相关(r=0.886,P<0.05),表明溶磷泛菌D2分泌的乙酸对无机磷的溶解有明显的促进作用,这也很可能是该菌株的重要溶磷机制之一.     

Growth and butyric acid production by Clostridium populeti

The growth of Clostridium populeti in 2% (w/v) glucose medium containing 0.2% (w/v) yeast extract was optimal with 10 mM NH₄Cl as the nitrogen source. Although the maximum specific growth rate (=0.32 h^-1) with 5 mM NH₄Cl was similar, the biomass yield was about 30% lower than that at the optimum. Either sodium sulphide or cysteine-HCl at an optimum concentration of 0.33 mM and 5.0 mM respectively, could serve as the sole sulphur source for growth. The growth rate was unaffected by initial glucose concentrations of up to 10% (w/v), but in the presence of 15% glucose it declined by about 35%. The molar yield of butyric acid (mol/mol glucose) declined from 0.70 in 1% (w/v) initial glucose medium to 0.39 in 10% glucose medium. In 5.7% initial glucose medium, butyric acid levels of 6.3 g/l were obtained (0.56 mol butyrate/mol glucose) after 72 h of incubation in 2.5 l batch cultures. A decrease of about 50% in the maximum specific growth rate of C. populeti was observed in the presence of an initial concentration of either 1.2 g/l of butyric acid or 18.9 g/l of acetic acid.This paper is issued as NRCC No. 29032     

Effect of malic acid on the growth kinetics of<Emphasis Type="Italic"> Lactobacillus plantarum</Emphasis>

The fermentation kinetics of Lactobacillus plantarum were studied in a specially designed broth formulated from commercially available, dehydrated components (yeast extract, trypticase, ammonium sulfate) in batch and continuous culture. During batch growth in the absence of malic acid, the specific growth rate was 0.20 h^–1. Malic acid in the medium, at 2 mM or 10 mM, increased the specific growth rate of L. plantarum to 0.34 h^–1. An increase in the maximum cell yield due to malic acid also was observed. Malic acid in the medium (12 mM) reduced the non-growth-associated (maintenance energy) coefficient and increased the biomass yield in continuous culture, based on calculations from the Luedeking and Piret model. The biomass yield coefficient was estimated as 27.4 mg or 34.3 mg cells mmol^–1 hexose in the absence or presence of malic acid, respectively. The maintenance coefficient was estimated as 3.5 mmol or 1.5 mmol hexose mg^–1 cell h^–1 in the absence or presence of malic acid. These results clearly demonstrate the energy-sparing effect of malic acid on the growth- and non-growth-associated energy requirements for L. plantarum. The quantitative energy-sparing effect of malic acid on L. plantarum has heretofore not been reported, to our knowledge.     

Culture conditions for growth and solvent biosynthesis by a modified Clostridium acetobutylicum

Summary A modified strain of Clostridium acetobutylicum and the fermentation medium conditions for good growth of the culture and normal production of solvents are described. The pretreatment of the culture with butyric-acid-enriched medium increased the final solvent yield on sugar and lowered the residual butyric acid accumulation. In a complex medium, relatively high concentrations of yeast extract (7.5 g/l) and ammonium sulphate (3 g/l to 6 g/l) were required for normal solvent synthesis. The nitrogen requirements for cellular growth and solvent production were distinctively different. Production of solvents and growth of the culture were dependent on the concentration of para-aminobenzoic acid and relatively independent of the variations of the initial pH of the medium in the range of 4.6 to 6.3. Solvent production was obtained with initial glucose concentrations of 20.5 g/l to 70 g/l, resulting in a maximum solvent concentration of 22 g/l and a maximum yield on glucose of 32.7%.     

氮源对灵芝菌丝体液态深层发酵合成灵芝三萜的影响

以沪农灵芝1号为供试菌株,葡萄糖作为碳源,用硫酸铵、氯化铵、鱼粉蛋白胨、胰蛋白胨和酵母粉作为氮源,研究不同种类氮源对灵芝菌丝体液态深层发酵过程的影响。首先,确定了N-10酵母自溶粉作为发酵的氮源,降低了发酵的复杂性和不确定性;其次,考察N-10酵母自溶粉不同浓度对灵芝菌丝体发酵合成灵芝三萜过程中菌丝体的生物量、葡萄糖消耗、灵芝三萜产量等方面的影响,确定了N-10酵母自溶粉的适宜添加浓度。在此基础上,采用响应面中心组合设计,对4因素最佳水平范围进行研究,结果表明,葡萄糖、N-10酵母自溶粉、磷酸二氢钾和七水硫酸镁的含量分别为31.06g/L、2.76g/L、1.77g/L和1.99g/L时,灵芝三萜的理论产量为21.166g/kg干菌丝体,实际发酵产量提高到21.153g/kg干菌丝体。与原工艺相比,新工艺的灵芝三萜产量提高了6.22%。     

Production of acetic acid by Acetogenium kivui

Summary The formation of acetic acid by the thermophilic nonsporeforming homoacetogenic bacterium Acetogenium kivui was studied under various conditions. In pH-controlled batch fermentation at pH 6.4 this bacterium was able to produce up to 625 mM of acetic acid from glucose within 50–60 h. The value of _max obtained was about 0.17 h^-1, the yield was about 2.55 mol of acetic acid per mol of glucose utilized. In continuous fermentation both substrate concentration and dilution rate (D) influenced the yield of acetate and the stationary concentration: a glucose concentration of 67 mM at D=0.09 h^-1 resulted in 2.82 mol acetate/mol glucose and 190 mM acetate at a production rate of 17.1 mM/1 h. When the dilution rate was increased the production rate reached a maximal value of 43.2 mM/1 h at D=0.32 h^-1. At a glucose concentration of 195 mM the dependence of yield upon dilution rate followed a similar pattern and an acetate concentration of 420 mM could be obtained. Enzymatic studies indicate that in A. kivui pyruvate ferredoxin-oxidoreductase and acetate kinase are inhibited at acetate concentrations higher than 800 mM. Based on these results a fed-batch fermentation was developed, which allowed to produce more than 700 mM acetic acid within 40–50 h.Dedicated to Prof. Dr. H. J. Rehm on the occasion of his 60th birthday     

Fermentative production of spiramycins

Fermentative production of spiramycins by Streptomyces ambofaciens has been performed using fermentation media of different chemical compositions. Medium I was selected from nine media as the best for production of high titres of spiramycins. Biochemical changes which occurred during fermentative production of spiramycins revealed that adjustment of the initial pH value of the medium was very important. The initial pH value of the fermentation medium which allowed the organism to produce a good yield of antibiotic was 6.5. The fermentation period affected the formation of spiramycins, and the maximum incubation period required for the fermentation process was 120 h. The role of inoculum on spiramycin yield showed that it was better to inoculate the fermentation medium with vegetative cells of Streptomyces ambofaciens rather with spores. The carbon source influenced spiramycin biosynthesis: dextrin was the best carbon source and stimulated the organism to form high titres of antibiotics. The best concentrations of dextrin and glucose for increased antibiotic yields were 25 and 15 gl^?1, respectively. Organic sources in the fermentation medium were more efficient than inorganic nitrogen sources for spiramycin formation. Fodder yeast was the best organic nitrogen source in fermentative production of spiramycins. The maximal concentrations of fodder yeast, soybean meal, peptone, Ca(NO₃)₂ and NH₄NO₃ for increased antibiotic yield were 6.5, 6.0, 4.0, 10.0 and 4.0 gl^?1, respectively.     

丙酮丁醇梭菌XY16丁醇发酵特性

以诱变选育的1株突变菌株丙酮丁醇梭菌XY16为对象,对影响该菌发酵特性的相关因素(N源、生长因子、热激)进行研究。结果显示:无机N源乙酸铵比其他N源更有利于丙酮丁醇的发酵,玉米浆或玉米蛋白可以直接替代生长因子进行丙酮丁醇发酵,热激可以提高总溶剂产量,最高可以达到21.28 g/L。该菌还可以同时利用葡萄糖和木糖,当葡萄糖利用完后,木糖才能被有效利用。     

Influence of dilution rate on the morphology and technological properties ofLactobacillus delbrueckii subsp.bulgaricus

Lactobacillus delbrueckii subsp.bulgaricus ATCC 11842 was grown in a chemostat at 45°C and pH 5.5 using glucose as the carbon source, with the aim of optimizing biomass production. Cells were grown in a complex medium under nitrogen. At dilution rates lower than 0.18h^–1, it was difficult to keep steady-state conditions and pleomorphic forms were observed. The addition of 30mM Ca²⁺ and Mn²⁺ reverted the cells to normal shape: 30mM Mg²⁺ had no effect. Increasing the dilution rate resulted in normal morphology without the addition of any cations. Under these conditions, a maximum productivity of 1.24g dry biomass 1^–1 h^–1 was obtained. The maximum growth yield, corrected for maintenance, was 30g biomass mol^–1 glucose and the maintenance energy was 0.26g glucose g^–1 biomass h^–1. Lactate was the main fermentation product at all glucose concentrations used in the fed medium. Cells grown at high dilution rates had normal technological properties (acid production and proteolysis) when tested in milk.     

Continuous acetone-butanol-ethanol fermentation using SO2-ethanol-water spent liquor from spruce

SO₂–ethanol–water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79 g/l using 4-fold diluted SEW liquor supplemented with 35 g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12 g/l was obtained at a dilution rate of 0.21 h⁻¹. The maximum solvent productivity (4.86 g/l h) with yield of 0.27 g/g was obtained at dilution rate of 0.64 h⁻¹. Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation.     

Biotechnological production of lactic acid integrated with fishmeal wastewater treatment by <Emphasis Type="Italic">Rhizopus oryzae</Emphasis>

Fishmeal wastewater, a seafood processing waste, was utilized for production of lactic acid and fungal biomass by Rhizopus oryzae AS 3.254 with the addition of sugars. The 30 g/l exogenous glucose in fishmeal wastewater was superior to starch in view of productivities of lactic acid and fungal biomass, and COD reduction. Fishmeal wastewater can be a replacement for peptone which was the most suitable nitrogen source for lactic acid production among the tested organic or inorganic nitrogen sources. Exogenous NaCl (12 g/l) completely inhibited the production of lactic acid and fungal growth. In the medium of COD 5,000 mg/l fishmeal wastewater with the addition of 30 g/l glucose, the maximum productivity of lactic acid was 0.723 g/l h corresponding to productivity of fungal biomass 0.0925 g/l h, COD reduction 84.9% and total nitrogen removal 50.3% at a fermentation time of 30 h.     

Tea stalks – a novel agro-residue for the production of tannase under solid state fermentation by Aspergillus niger JMU-TS528

A novel agro-residue, tea stalks, was tested for the production of tannase under solid-state fermentation (SSF) using Aspergillus niger JMU-TS528. Maximum yield of tannase was obtained when SSF was carried out at 28 °C, pH 6.0, liquid-to-solid ratio (v/w) 1.8, inoculum size 2 ml (1?×?10⁸ spores/ml), 5 % (w/v) ammonium chloride as nitrogen source and 5 % (w/v) lactose as additional carbon source. Under optimum conditions, tannase production reached 62 U/g dry substrate after 96 h of fermentation. Results from the study are promising for the economic utilization and value addition of tea stalks.     

Fermentation and recovery of glutamic acid from palm waste hydrolysate by Ion-exchange resin column

Glutamic acid produced from palm waste hydrolysate by fermentation with Brevibacterium lactofermentum ATCC 13869 is produced with a remarkably high yield compared with that produced from pure glucose as a carbon source. The produce yield is 70 g/L with glucose, wherease, when palm waste hydrolysate is the fermentation medium in the same bioreactor under same conditions, it is 88 g/L. The higher yield may be attributed to the fact that this organism has the ability to convert sugars other than only glucose present in the hydrolysate. Bioreactor conditions most conducive for maximum production are pH 7.5, temperature of 30 degrees rmentation period of 48 h, inoculum size 6%, substrate concentration of 10 g per 100 mL, yeast extract 0.5 g per 100 mL as a suitable N source, and biotin at a concentration of 10 pg/L. Palm waste hydrolysate used in this study was prepared by enzymic saccharification of treated palm press fiber under conditions that yielded a maximum of 30 g/L total reducing sugars. Glutamic acid from fermentation broth was recovered by using a chromatographic column (5cm x 60 cm) packed with a strong ion-exchange resin. The filtered broth containing glutamic acid and other inorganic ions was fed to the fully charged column. The broth was continuously recycled at a flow rate of 50 mL/min (retention time of 55 min) until glutamic acid was fully adsorbed on the column leaving other ions in the effluent. Recovery was done by eluting with urea and sodium hydroxide for total displacement of glutamic acid from the resin. The eluent containing 88 g/L of glutamic acid was concentrated by evaporation to obtain solid crystals of the product. (c) 1995 John Wiley & Sons, Inc.