Use of waste Chinese cabbage as a substrate for yeast biomass production

The possibility of using waste Chinese cabbage (Brassica campestris) as a substrate for microbial biomass production was investigated. The juice from waste Chinese cabbage contains relatively high amounts of reducing sugars suitable for yeast culture. The cell mass and protein content of four species of yeast, Candida utilis, Pichia stipitis, Kluyveromyces marxianus, and Saccharomyces cerevisiae, were determined when cultured in juice extracted from cabbage waste. Compared to YM broth containing the same level of sugar, all the strains except C. utilis showed higher total protein production in cabbage juice medium (CJM).     

Inhibition of the growth of Candida utilis by certain heavy metals

The effect of Zn2+, Mn2+, Cd2+ and Hg2+ ions on the kinetics of growth was studied with Candida utilis. The inhibition of Candida utilis growth by Zn2+ and Mn2+ ions is described by the equation for noncompetitive inhibition of enzymatic reactions which is not the case with Cd2+ and Hg2+ ions. The inhibition constants (Ki) for these metals have been determined.     

激光复合诱变选育叶酸高产菌

利用高效液相色谱测定发酵液中叶酸含量,比较产朊假丝酵母(Candida utilis)、异常汉逊酵母(ftan-senula anomala)和枯草芽孢杆菌(Bacillus subtilis)产叶酸能力的高低,从而确定生产叶酸的最佳菌种.出发菌株经紫外照射诱变后,再采用激光复合诱变方式进行进一步的筛选,并对其传代稳定性进行研究,以期进一步获得稳产高产叶酸产生菌突变株.结果表明产朊假丝酵母产叶酸量最高.紫外照射3 min得到的Y1.4菌株产叶酸量与原始菌株相比,产量提高了33.8%.激光一紫外复合诱变后筛选出4株产量较高的菌株,其中以Y2.12产量最高.Y2.12产叶酸量与原始菌株相比,提高了65.8%.经传代培养分析,Y2.12诱变株的产量稳定.该结果表明,激光复合诱变是获得高产叶酸的有效途径.     

响应面法优化产朊假丝酵母培养及干燥工艺

本研究旨在优化产朊假丝酵母液体培养参数及干燥保护剂配方,提高产朊假丝酵母液体培养数量,制备出高复苏率的活性干酵母。以装液量、转速、温度和培养时间为影响因素,设计单因素试验,并采用Box-Behnken试验设计及响应面分析法优化产朊假丝酵母液体培养方案。在此条件下培养酵母,以L-谷氨酸钠、乳糖、脱脂奶粉为影响因素进行单因素保护试验,并采用响应面分析法优化干燥保护剂的组合。结果表明,产朊假丝酵母最佳培养条件为装液量45 mL/250 m L,转速200 r/min,温度30℃,培养时间24 h。在此条件下,培养的产朊假丝酵母数量可以达到9.34×10~8CFU/mL;最佳保护剂组合1%L-谷氨酸钠、12%脱脂奶粉、6%乳糖,经干燥后,产朊假丝酵母复苏率达到81.9%。此时活菌数7.65×10~8CFU/g,比未加保护剂组提高了3.83倍。     

Studies on the growth of Candida utilis on d-galacturonic acid and the products of pectin hydrolysis

Candida utilis was found to utilize d-galacturonic acid for cell growth, the incubation conditions being similar to those reported for growth on other substrates. At concentrations of d-galacturonic acid below 3 g l⁻¹cell yields were similar to those obtained using glucose, although at higher concentrations cell yields were reduced. Small, regular increases in the concentration of d-galacturonic acid substantially increased cell yields under the incubation conditions employed. Poly-d-galacturonic acid, hydrolysed by a fungal polygalacturonase [poly(1,4-α-d-galacturonide) glycanohydrolase, EC 3.2.1.15] prior to cell growth, yielded 27 g C. utilis cells/100 g substrate. Acid-hydrolysed pectin yielded 23 g cells/100 g substrate but no cell growth was found using pectin which had been degraded by alkali. The possibility of using pectin materials for the production of singlecell protein in a modified Symba process is discussed.     

Relationship between growth inhibition and mitochondrial function in petite-negative yeasts. I. Effects of antibiotics and dyes upon pathogenic and non-pathogenic Candida species

Antibiotics and dyes which preclude growth of Saccharomyces cerevisiae in media containing oxidizable carbon sources arrested the growth of Candida albicans, Candida tropicalis and Candida utilis even in glucose medium. The growth in the presence of sub-inhibitory concentrations of the various antibiotics and dyes determined a reduction in the cell survival but with no accumulation of respiratory deficient mutants. Under these culture conditions, the total respiration declined leaving a residual antimycin A-resistant--hydroxamate-sensitive O2 uptake, and the amount of the respiratory cytochromes aa3 and b synthesized was reduced. SDS gel electrophoresis of soluble proteins prepared from the antibiotic-treated cells showed some bands in the MW range 92-100 K, which became faint after the cells were grown in the presence of some mitochondrial inhibitors. The ultrastructural analysis of these cells evidenced disappearance of the mitochondrial cristae and their replacement by unfolded membranes. The data obtained suggest that the petite negative trait of Candida could depend on the non-viability or on the very low viability of those cells which have lost their mitochondrial function.     

玉米秸秆和异Vc钠生产废液固态发酵生产高蛋白饲料研究

以玉米秸秆为原料,以麸皮和异Vc钠生产废液(WEP)为辅料进行生物蛋白饲料固态发酵研究.通过菌种配伍试验,确定了混菌发酵菌种为白地霉、产朊假丝酵母和枯草芽孢杆菌.在此基础上通过单因素优化试验确定了秸秆蛋白饲料的最优发酵条件:以玉米秸秆(5 g)和麸皮(1 g)为基料,4%WEP营养液,固液比1:4(g/mL),初始pH值4.5;以麸皮浸汁作种子培养液,种龄24 h,各菌接种比例为产朊假丝酵母∶白地霉∶枯草芽孢杆菌=3:1:1,接种量2 mL;28℃、静置发酵2 d,在此条件下,秸秆饲料中真蛋白含量为6.21%,比对照提高了23.95%.该研究为秸秆和异Vc钠生产废液的高质化利用提供了新的思路和途径.     

A biochemical explanation for lipid accumulation in Candida 107 and other oleaginous micro-organisms.

The biochemical explanation for lipid accumulation was investigated principally in Candida 107 and, for comparison, in the non-oleaginous yeast Candida utilis. There were no significant differences between these two yeasts in their control of glucose uptake; in both yeasts, the rates of glucose uptake were independent of the growth rate and were higher in carbon-limited chemostat cultures than in nitrogen-limited cultures. There was no lipid turnover in either yeast, as judged from [14C]acetate uptake and subsequent loss of 14C from the lipid of steady-state chemostat cultures. Acetyl-CoA carboxylase from both yeasts was similar in most characteristics except that from Candida 107 was activated by citrate (40% activation at 1 mM). The enzyme from Candida 107 was relatively unstable and, when isolated from nitrogen-limited (lipid-accumulating) cultures, was accompanied by a low molecular weight inhibitor. The reason for lipid accumulation is attributed to the decrease in the intracellular concentration of AMP as cultures become depleted of nitrogen. As the NAD+-dependent isocitrate dehydrogenase of Candida 107, but not C. utilis, requires AMP for activity, the metabolism of citrate through the tricarboxylic acid cycle in the mitochondria becomes arrested. In Candida 107, but not in C. utilis, there is an active ATP:citrate lyase which converts the accumulating citrate, when it passes into the cytosol, into acetyl-CoA and oxaloacetate. The former product is then available for fatty acid biosynthesis which is stimulated by the high ATP concentration within the cells, by the activation of acetyl-CoA carboxylase by citrate and by the provision of NADPH generated as oxaloacetate is converted via malate to pyruvate. Similar characteristics were evident in oleaginous strains of Rhodotorula glutinis and Mucor circinelloides but not in non-oleaginous representatives of these species.     

HPLC purification of the natural ATPase inhibitor from the yeast Candida utilis

A rapid method of preparation of the natural ATPase inhibitor (IF1) from the mitochondria of the yeast Candida utilis has been developed. It involved high performance liquid chromatography (HPLC) as the final step of purification. An active form of Candida utilis IF1 was obtained free of contaminant. Its properties are compared with those of IF1 from other sources.     

Influence of specific growth rate on biomass yield, productivity, and compostion of Candida utilis in batch and continuous culture.

Candida utilis was grown in batch and continuous culture on prickly pear juice as sole carbon and energy source. In batch culture the maximum specific growth rate (mum) and the substrate yield coefficient (Yps) varied according to sugar concentration. When the fermentation was carried out with 1% sugar, mum and Ys were 0.47/h and 42.6%, respectively. The best yields occurred in a chemostat at the pH range of 3.5 to 4.5 and temperature of 30 C. A beneficial effect on Ys was observed when the dilution rate (D) was increased. At a D of 0.55/h, the productivity was 2.38 g/liter per h. The maintenance coefficient attained a value of 0.09 g of sugar/g of biomass per h. Increases of D produced higher protein contents of the biomass. The information obtained indicates that protein production with Candida utilis, using prickly pear juice, should be carried out a high dilution rates where the Ys and protein content of the cell mass are also higher.     

产朊假丝酵母(Candida utilis)基因工程研究进展

产朊假丝酵母是生物安全(Generally Recognized as Safe,GRAS)的微生物,也是一种重要的工业微生物。近20年来,随着分子生物学技术的发展,产朊假丝酵母的基因表达系统和基因工程研究及开发应用取得了显著的进展,使得利用该菌表达多种物质成为可能。本文概述了产朊假丝酵母的生物学特点、外源基因表达系统、基因敲除、遗传转化等方面的研究和应用进展。     

Cross-action of extracellular stress adaptation factors in microorganisms]

The capacity of microorganisms from different taxa to adapt to stress conditions with the help of extracellular factors exhibiting similar mechanisms of action was demonstrated. The action of adaptation factors synthesized by the enteric bacterium Escherichia coli, the soil bacterium Bacillus subtilis, and the yeast Candida utilis was characterized in biological tests. It was demonstrated that the factor of accelerated adaptation to new media (FAANM) and the growth-rate-reducing factor (factor X(II)), which decreases the rate of exponential culture growth, were synthesized by all microorganisms tested. Antilysin (factor X(I)), which accelerates cell adaptation to N-ethylmaleimide, was not produced by C. utilis.     

Influence of specific growth rate on biomass yield, productivity, and compostion of Candida utilis in batch and continuous culture.

Candida utilis was grown in batch and continuous culture on prickly pear juice as sole carbon and energy source. In batch culture the maximum specific growth rate (mum) and the substrate yield coefficient (Yps) varied according to sugar concentration. When the fermentation was carried out with 1% sugar, mum and Ys were 0.47/h and 42.6%, respectively. The best yields occurred in a chemostat at the pH range of 3.5 to 4.5 and temperature of 30 C. A beneficial effect on Ys was observed when the dilution rate (D) was increased. At a D of 0.55/h, the productivity was 2.38 g/liter per h. The maintenance coefficient attained a value of 0.09 g of sugar/g of biomass per h. Increases of D produced higher protein contents of the biomass. The information obtained indicates that protein production with Candida utilis, using prickly pear juice, should be carried out a high dilution rates where the Ys and protein content of the cell mass are also higher.     

Growth of Candida utilis on distillery effluent

Summary A Candida utilis isolate was adapted to growth on distillery stillage from sugarcane molasses and used for production of single cell protein from the effluent. The nonfermentable sugars in the effluent were completely utilised during the growth of the organism and the BOD value of the effluent was reduced to 17% of the original value.     

Effect of cyclic changes in culture conditions on the growth kinetics and physiological characteristics of yeasts

Candida utilis, Saccharomyces cerevisiae and Candida scottii were used to study the effect of cyclic changes in the pH and pO2 within a range of 1 to 60 min on their growth kinetics and physiological properties. These changes were shown to increase the specific growth rate from 0.33 to 0.5-0.6 h-1 without decreasing the economic coefficient and the quantity of budding cells during 2-3 generations of the exponentially growing batch culture of C. utilis. Optimal conditions of cyclic changes in the pO2 (minutes) were found to increase the specific growth rate of C. scottii and S. cerevisiae. The authors discuss a hypothesis for the formation of intermediate products in the substrate oxidation in the course of pulse aeration by the yeasts during the aerobic stage and the utilization of the products at the anaerobic stage of cyclic regimes. The paper describes a mathematical model for the yeast growth under the nonsteady-state conditions of pH and pO2, which accounts for the formation and utilization of possible intermediate biosynthetic products within the studied time intervals.     

Growth of Aureobasidium pullulans on straw hydrolysate.

Growth characteristics and cell properties of Aureobasidium (Pullularia) pullulans were studied. The organism grew well on an acid hydrolysate of ryegrass straw over a wide range of pH and temperature. The optimum temperature and pH for the growth of the organism were 32 degrees C and 5.5, respectively. A cell yield of 1.5 g/liter of straw hydrolysate was obtained. The dried cell mass contained 42.6% crude protein, 0.4% crude fat, and 6.4% nucleic acids. The essential amino acid profile of the microbial protein was comparable to that of Candida utilis. A rat feeding study indicated that the A. pullulans cells were not toxic and that the feed intake, weight gain, and protein efficiency ratio values were superior to those obtained with C. utilis. Once the question of mathogenicity is resolved, A. pullulans could be useful for production of single-cell protein from cellulosic wastes.     

Growth of Aureobasidium pullulans on straw hydrolysate.

Growth characteristics and cell properties of Aureobasidium (Pullularia) pullulans were studied. The organism grew well on an acid hydrolysate of ryegrass straw over a wide range of pH and temperature. The optimum temperature and pH for the growth of the organism were 32 degrees C and 5.5, respectively. A cell yield of 1.5 g/liter of straw hydrolysate was obtained. The dried cell mass contained 42.6% crude protein, 0.4% crude fat, and 6.4% nucleic acids. The essential amino acid profile of the microbial protein was comparable to that of Candida utilis. A rat feeding study indicated that the A. pullulans cells were not toxic and that the feed intake, weight gain, and protein efficiency ratio values were superior to those obtained with C. utilis. Once the question of mathogenicity is resolved, A. pullulans could be useful for production of single-cell protein from cellulosic wastes.     

Enzymatic saccharification of pretreated rice straw and biomass production

A comparative study on the saccharification of pretreated rice straw was brought about by using cellulase enzyme produced by Aspergillus terreus ATCC 52430 and its mutant strain UNGI-40. The effect of enzyme and substrate concentrations on the saccharification rate at 24 and 48 were studied. A syrup with 7% sugar concentration was obtained with a 10% substrate concentration for the mutant case, whereas a syrup with 6.8% sugar concentration was obtained with 3.5 times concentrated enzyme from the wild strain. A high saccharification value was obtained with low substrate concentration; the higher the substrate concentration used, the lower the percent saccharification. The glucose content in the hydrolysate comprised 80-82% of total reducing sugars; the remainder was cellobiose and xylose together. The hydrolysate supported the growth of yeasts Candida utilis and Saccharomyces cerevisiae ATCC 52431. A biomass with a 48% protein content was obtained. The essential amino acid composition of yeast biomass was determined.     

The relation between the assimilation of methanol and glycerol in yeasts

Fifteen yeast strains of the genera Candida, Lodderomyces, Endomycopsis, Saccharomyces, Hansenula, Pichia and Torulopsis were investigated with respect to their ability to grow on methanol, glycerol and glucose as sole carbon and energy source. Eight of them can grow on both methanol and glycerol.Methanol is assimilated via triosephosphate (dihydroxyacetone) pathway. The dihydroxyacetone kinase is a key enzyme in methanol metabolism.The assimilation of glycerol can take place in bacteria via a phosphorylative or/and oxidative pathways. In general, the phosphorylative pathway is found in eucaryotes. In the present paper it is shown that in yeasts, which can utilize methanol and glycerol, too, glycerol is assimilated via an oxidative pathway, Dihydroxyacetone is a central intermediate in the assimilation of methanol as well as glycerol. It is metabolized by means of the dihydroxyacetone kinase.The enzyme formed during growth of Candida methylica on methanol does not differ from that of Candida valida H 122 after growing on glycerol as far as the regulatory properties are concerned.     

Protein enrichment of potato processing waste through yeast fermentation

Potato starch obtained from waste waters of chips manufacturing was used as a fermentation substrate for yeast protein enrichment. Among 18 yeast strains, 6 strains were screened according to their biomass yield and protein content after fermentation for 16 h at 30 degrees C in an aerated glucose-based liquid media (4.5 Ls). Using concentrated media (25% solids) made from potato starch pre-hydrolyzed with malt flour and batch-fermented for 20 h at 26 degrees C under aerobic conditions, Candida utilis ATCC 9256 was the most efficient protein-forming strain. Scaled-up at the 100 Ls level, the aerobic batch process was improved under fed-batch conditions with molasses supplementation. After drying, fermented starch contained 11-12% protein, including 7-8% yeast protein.