富马酸生产菌少根根霉的诱变筛选

以实验室原少根根霉为出发菌种,通过紫外线和LiCl诱变处理,发现当紫外线照射时间为3min,并在质量分数4％LiCl的平板中培养,可诱变出富马酸高产菌。利用溴甲酚绿加塑料小管的平板进行初筛,其生成的富马酸通过塑料小管底部渗透到指示培养基中,产生变色圈,根据变色圈大小可初步判断诱变株的产酸能力,大大缩短了筛选时间。在葡萄糖质量浓度为80g/L时,诱变后的3#菌种在发酵72h后能产生55．02g/L的富马酸,比原菌种的富马酸产量提高了2．49倍。     

Optimization of fumaric acid production by Rhizopus delemar based on the morphology formation

The effects of temperature, agitation rate and medium composition, including concentrations of glucose, soybean peptone, and inorganic ions, on pellet formation and pellet diameter of Rhizopus delemar (Rhizopus oryzae) NRRL1526 during pre-culture were studied. Inorganic ions and soybean peptone had negative and positive effects on pellet formation, respectively. The initial glucose and soybean peptone concentrations directly affected pellet diameter. Within a certain range, pellet diameter decreased with increased initial substrate concentrations; however, above this range there was an opposite trend. Thus, optimal concentrations of substrate during pre-culture were beneficial for producing small pellets of R. delemar. Furthermore, dry cell mass and yield of fumaric acid tended to increase with decreased pellet diameter. Based on the pellet morphology optimization, the final fumaric acid concentration was improved by 46.13% when fermented in a flask and 31.82% in stirred bioreactor tank fermentation.     

Direct fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of direct fermentation for lactic acid production by fungal species of Rhizopus arrhizus 3,6017 and Rhizopus oryzae 2,062 was studied with respect to growth pH, temperature and substrate. The direct fermentation was characterized by starch hydrolysis, accumulation of reducing sugar, and production of lactic acid and fungal biomass. Starch hydrolysis, reducing sugar accumulation, biomass formation and lactic acid production were affected with the variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30°C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.87–0.97 g/g starch associated with 1.5–2.0 g/l fungal biomass produced in 36 h fermentation. R. arrhizus 3,6017 had a higher capacity to produce lactic acid, while R. oryzae 2,062 produced more fungal biomass under similar conditions.     

Physiological restriction of the L-lactic acid production by Rhizopus arrhizus

The influence of basic physiological factors on the quality of inocula and L(+)-lactic acid production by Rhizopus arrhizus CCM 81 09 were studied. The most effective preparation of the spores (5 × 10⁷ spores/ml) and subsequent good lactate production was achieved on the agar medium with soil extract and malt agar. The optimum initial amount of active spores for inoculation was 10³–10⁴ spores/ml. The preparation of inoculum required intensive stirring with lower aeration and pH maintained in the range from 4.8 to 6.0 by the addition of CaCO₃. The maximum yield of lactic acid production was achieved by using 5% (v/v) of 24-h-old inoculum. The intensity of lactic acid production in the inoculum was proportional to its production in the subsequent steps of fermentation and can be used as a fast control of the physiological state of the producers.     

Comparison of fumaric acid production by Rhizopus oryzae using different neutralizing agents

Fumaric acid fermentation in a 10-L bubble column fermenter using different neutralizing agents [CaCO(3), Ca(OH)(2), NaHCO(3)] by Rhizopus oryzae ATCC 20344 was examined. It was found that in the fermentation using CaCO(3 )as the neutralizing agent the highest fumaric acid weight yield and volumetric productivity were obtained, 53.4% and 1.03 g/L x h(-1) respectively. In the NaHCO(3) case, the fumaric acid weight yield and volumetric productivity were 33.7% and 0.69 g/L x h(-1), respectively, much lower than the CaCO(3) case. However, the NaHCO(3) alternative has advantages of cell reuse and simple downstream processing because of the high solubility of sodium fumarate. These advantages may offset the disadvantages of using NaHCO(3) as the neutralizing agent, and the overall fumaric acid weight yield and volumetric productivity will increase.     

Influence of carbohydrates and polyols on l-lactic acid production and fatty acid formation by Rhizopus arrhizus

Growth and l-lactic acid production on 24 different carbohydrates and polyols (glycerol, mannitol and sorbitol) by Rhizopus arrhizus CCM 8109 were determined. The d- but not the l-forms of xylose, fructose, galactose, mannose, glucose, cellobiose, maltose and sucrose and partially hydrolysed starch were converted to l-lactic acid. Changes in lipid formation and fatty acid composition were detected in biomass grown on the different sugars. In the presence of polyols, growth and considerable production of lipids were observed with little or no lactate production. Invertase was mainly associated with the mycelium during growth on sucrose, whereas glucoamylase and -amylase were produced extracellularly during growth on starch.The authors are with the Department of Biochemical Technology, Faculty of Chemical Technology, Slovak Polytechnical University, Radlinského 9, SK-812 37 Bratislava, Slovak Republic     

米根霉ME—F12发酵产富马酸的菌体形态控制

丝状真菌发酵体系中菌体形态对产量有着重要影响。考察富马酸产生菌Rhizopus oryzae ME—F12种子培养过程中不同pH条件、孢子悬浮液密度以及CaCl2添加量对其形态的影响。结果表明,当控制种子培养液pH2．3～2．7、接种孢子的终密度为1．5×10^8～3．0×10^8／L和添加0．5g／LCaCl2时,培养可获得直径约为0．65mm光滑规整茵球,后继的产酸发酵中富马酸量高达58．9g／L。正交实验表明,pH是影响菌球形成的最主要因素,孢子液密度主要影响菌体生物量,而CaCl2则是菌球表面光滑度的主要影响因素。     

少根根霉原变种发酵生产薯蓣皂苷元

从穿龙薯蓣Dioscorea nipponica中分离得到的一少根根霉原变种Rhizopus arrhizus var. arrhizus菌株,能实现薯蓣皂苷的生物转化。用该菌株发酵穿龙薯蓣D. nipponica生产薯蓣皂苷元,采用高效液相色谱法测定薯蓣皂苷元的含量,其总得率可达3.00%。运用该菌株发酵制备薯蓣皂苷元,操作简单,环保,且得率高。     

Development of a low pH fermentation strategy for fumaric acid production by Rhizopus oryzae

Dicarboxylic acids that are produced from renewable resources are becoming attractive building blocks for the polymers industry. In this respect, fumaric acid is very interesting. Its low aqueous solubility facilitates product recovery. To avoid excessive waste salt production during downstream processing, a low pH for fumaric acid fermentation will be beneficial. Studying the influence of pH, working volume and shaking frequency on cell cultivation helped us to identify the best conditions to obtain appropriate pellet morphologies of a wild type strain of Rhizopus oryzae. Using these pellets, the effects of pH and CO(2) addition were studied to determine the best conditions to produce fumaric acid in batch fermentations under nitrogen-limited conditions with glucose as carbon source. Decreasing either the fermentation pH below 5 or increasing the CO(2) content of the inlet air above 10% was unfavourable for the cell-specific productivity, fumaric acid yield, and fumaric acid titer. However, switching off the pH control late in the batch phase did not affect these performance parameters and allowed achieving pH of 3.6. A concentration of 20 gL(-1) of fumaric acid was obtained at pH 3.6 while the average cell mass specific productivity and fumaric acid yield were the same as at pH 5.0. Consequently, relatively modest amounts of inorganic base were required for pH control, while recovery of the acid should be relatively easy at pH 3.6.     

Production enhancement of Rhizopus arrhizus lipase by feeding oleic acid

A strategy for Rhizopus arrhizus lipase production enhancement by feeding oleic acid was developed. The oleic acid was proved to have strong inducing effect on lipase production, but high concentration oleic acid could repress lipase production. The decrease rate of oleic acid concentration using peanut oil as initial carbon source was figured out according to the change of oleic acid concentration in the fermentation broth. Our feeding strategy designed based on the decrease rate of oleic acid could avoid the repression of lipase production that is caused by high concentration of oleic acid in the fermenting liquor, and this strategy worked as a new feeding method showing excellent performance. The maximum lipase activity was gained by feeding dilute oleic acid every 12 h starting at 60 h, which maintained the oleic acid concentration around 18 mg/L, and the lipase activity was 31% higher than that of no feeding.     

Direct ammonium fumarate production by Rhizopus arrhizus under phosphorous limitation

Direct ammonium fumarate production from glucose-based media with Rhizopus arrhizus NRRL 1526 was obtained using 2-kmol (NH₄)₂CO₃ per-m³ as neutralising agent and controlling mycelial growth by phosphorous (P) limitation. As the P level in the production medium was increased from 0 to 0.3-kg of KH₂PO₄ per m³, the fumarate yield decreased from 0.32 to 0.13-g per-g of glucose consumed; maximum ammonium fumarate productivity (0.46-kg-m^–3-h^–1) was obtained when using 0.1-kg phosphate-m^–3.     

Biosorption of radionuclides by Rhizopus arrhizus

The sorption of various radionuclides viz. 233U, 239Pu, 241Am, 144Ce, 147Pm, 152+154Eu and 95Zr from aqueous nitrate medium has been studied using biomass Rhizopus arrhizus. The biosorption of 233U and 239Pu was found to be maximum at pH 6-7 whereas for other trivalent actinides and fission products viz. 241Am, 144Ce, 147Pm, 152+154Eu and tetravalent 95Zr, it was more effective at pH 2. This biomass is a promising sorbant for the treatment of radioactive effluents from nuclear industry. © Rapid Science Ltd. 1998     

基于Desirability函数法对米根霉发酵制备富马酸的多目标优化

以富马酸产量和生产速率为目标,通过正交实验考察了种龄,接种量,葡萄糖和尿素浓度对两者的影响,进一步利用基于响应曲面方法的Desirability函数确定了葡萄糖和尿素的最佳浓度。结果表明,最佳的种龄和接种量分别为36h和15%,葡萄糖和尿素的优化浓度为132.73和0.0586g/l,此时模型预测的富马酸产量和生产速率达到71.42g/l和0.804g/(l.h),Desirability的函数值高达0.966。该条件下在5L发酵罐水平上进行验证试验,经过88h的发酵最终生成富马酸66.5g/l,生产速率达到0.755 g/(l.h),与未优化前相比,产量和生产速率分别提高了13.9%和15.8%,取得了理想的效果,实现了产量和生产速率的同时优化,为发酵法制备富马酸的工业化放大奠定了基础。     

Lipids of Rhizopus arrhizus Fischer

The lipids of Rhizopus arrhizus Fischer mycelia and sporangiospores were extracted, isolated, and separated by thin-layer, liquid, and gas chromatography. Structural confirmations of the compounds were made by a gas chromatographmass spectrometer combination. The n-heptane fraction contained squalene (1%) as a major hydrocarbon constituent. Other major lipid classes detected were free fatty acids, naturally occurring methyl esters of fatty acids, triglycerides, sterols, and polar lipids. The polar lipids (44.4%) were found in the highest concentrations, and the triglycerides (22.1%), sterols (16.7%), and free fatty acids (11.7%) were present in lesser concentrations. This is the first report of naturally occuring methyl esters of long-chain fatty acids being present in fungal mycelium. There appears to be a preference for incorporation of unsaturated acids into the complex lipids, with the exception of the triglycerides. The major saturated fatty acids in the mycelium were palmitic (C(16)) and arachidic (C(20)), whereas the major unsaturated acids were oleic (C(18:1)) and linoleic (C(18:2)), respectively.