利用秸秆类物质进行微生物共发酵生产单细胞蛋白

本实验采用固液混合共发酵方式,对绿色木霉和饲料酵母在纤维素材料上共生发酵,生产单细胞蛋白质的条件进行了研究。研究发现,在木霉接种９６ｈ后再接种酵母,混合培养后,培养物中蛋白质含量提高到２０－２５％,并可获得３０％的单细胞蛋白,产物中蛋白质含量在５３％以上,且富含多种酶类、氨基酸及维生素等,从而提高了纤维素原料的营养价值,该法使纤维素转化率达５１％。     

利用微生物混合培养物生产沙棘果渣单细胞蛋白

以沙棘果渣作为唯一碳源进行了单细胞蛋白发酵研究。经过筛选,从４０多株霉菌、酵母菌和细菌中选育出Ｍｙ－９３１霉菌－酵母混合培养物能迅速地将沙棘果渣转变为单细胞蛋白。在最佳条件下,沙棘果渣经发酵后,其发酵产品粗蛋白含量达４４．１％。动物饲喂试验证明此发酵产品安全无毒,能部分替代鱼粉用作蛋白饲料。     

泥炭固体发酵生产单细胞蛋白研究

对以泥炭为唯一碳源,固体发酵生产单细胞蛋白(SCP)进行了一系列的研究。选用酵母菌和黑曲霉进行混合发酵培养,考察影响单细胞蛋白生产的各个因素,如菌种接种量,培养基含水量,发酵时间,发酵温度,培养基外加氮源等。通过正交实验设计确定了优化的培养条件。即:菌种接种量为10%,培养基含水量为300%,28℃培养72 h,以蛋白胨为氮源。     

混合菌发酵转化纤维素生产单细胞蛋白

纤维素是自然界中存在的最丰富的天然资源,合理开发和利用纤维素是科学家们一直致力于研究的重点领域.尽管几十年来人们在纤维素及纤维素酶的理论研究和实践应用方面均取得了较大进步,迄今尚无一种微生物或一套酶系按传统方法用于大规模降解纤维素,并取得显著经济效益[1-3].利用微生物混合发酵,可使纤维素转化为单细胞蛋白.该方面研究不仅可以解决蛋白资源短缺,解决动物饲料需求上的短缺,而且还可以提高和改善饲料中的蛋白含量和营养价值.本文就混合菌发酵转化纤维素合成单细胞蛋白的应用研究进行概述. 1 液态混合菌体系发酵纤维素合成单细胞蛋白     

利用多菌种混合发酵转化玉米秸秆的研究

该文系统地研究了高产纤维素酶生产菌（ＴｒｉｃｈｏｄｅｒｍａｒｅｓｉＴＢ９７０１）与饲料酵母混合共发酵玉米秸秆粉对合成菌体蛋白质和利用纤维素的关系,优选出一条最佳的共发酵工艺途径和条件。研究表明在以氨法处理的玉米秸秆为底物的ＴＢ－９７０１与饲料酵母菌的混合菌共发酵正交实验中,于ｐＨ５．０,３０℃的条件下２００ｒ／ｍｉｎ的恒温、恒速摇瓶培养８ｄ,经测定发酵液终产物中粗蛋白（ＳＣＰ）的含量达到了２３．７０％,总秸秆纤维的转化率达到７０％以上。     

万古霉素发酵废渣固态发酵生产单细胞蛋白的研究

以万古霉素发酵废渣为唯一培养基,对固态发酵生产单细胞蛋白(SCP)进行了研究.经过筛选得到了一株白地霉HCCB 2267,它能以万古霉素发酵废渣为唯一底物生长.通过菌株驯化和培养条件优化,固态发酵产生的SCP可迭9.42×108个/g干重,其粗蛋白含量达47.24%,氨基酸总量从30.60%提高到46.28%.其优化的培养条件是:培养基起始含水量60%,起始pH 5.0～6.0,接种量15%,培养温度28～30℃,培养时间72h等.此外,筛选到的菌株对废渣中残存的菌丝体有降解作用.     

圆盘式固态发酵器生产单细胞蛋白的研究

采用圆盘式固态发酵器生产单细胞蛋白(SCP)。发酵器有机械化上料、搅拌、补料、出料装置和自动调节温度、湿度、通风系统,单机日产量1吨。用SC₈₅;和ST₈₅₁,酵母以淀粉质原料,固态培养24h,产品粗蛋白含量由15．7％增加至40．50％以上(以干物质计),蛋氨酸含量接近鱼粉。该工艺培养条件稳定,产品质量可靠。表明圆盘式固态发酵器是一种性能良好的发酵器。     

以麦芽根为原料发酵生产单细胞蛋白研究初报

以麦芽根为原料发酵生产单细胞蛋白研究初报刘海滨（烟台大学生化系．烟台）单细胞蛋白（Ｓｉｎｇｌｅ－ｃｅｌｌｐｒｏｔｅｎ,ＳｃＰ）是近年来生物技术方面研究比较活跃的领域之一。与传统的蛋白质原料相比,单细胞蛋白具有蛋白质含量高、氨基酸组成齐全、富含维生素并...     

利用光合细菌发酵转化麸皮

研究了光合细菌不同处理下对麸皮分解转化的效果。设计8种处理方法：经氨化,未经氨化,分别进行好氧培养,厌氧培养,对照培养,未加光合菌室温下放置的4种不同操作。在处理的1d,2d,3d,5d时分别测定每个培养瓶中葡萄糖和蛋白质含量,并且调节其pH值在6．6－7．5之间,结果表明,光合细菌在经氨化的厌氧培养时对麸皮的转化效果最好。     

Conversion of cellulose into fungal cell mass

Summary Chaetomium cellulolyticum (ATCC 32319) was cultivated on glucose, Avicel and/or Sigmacell in a 20-1 stirred tank batch reactor. The substrate (cellulose) concentration, the cell mass concentration (through protein and/or nitrogen content), reducing sugar concentration, the enzyme activity, the alkali consumption rate, the dissolved O₂ and CO₂ concentrations in the outlet gas were measured. The specific growth rate, the substrate yield coefficient, cell productivity, the oxygen consumption rate, the CO₂ production rate and the volumetric mass transfer coefficient were determined. At the beginning of the growth phase the oxygen utilization rate exhibits a sharp maximum. This maximum could be used to start process control. Because of the long lag phase periodic batch operation is recommended.Symbols CP cell protein concentration (g l^–1) - FPA FP enzyme activity (IU l^–1) - GP dissolved protein concentration (g l^–1) - IU international unit of enzyme activity - k_La volumetric mass tranfer coefficient (h^–1) - LG alkali (1 n NaOH) consumption (ml) - LGX specific alkali consumption rate per cell mass (ml g^–1 h^–1) - P cell mass productivity (g l^–1 h^–1) - specific oxygen consumption rate per cell mass (g g^–1 h^–1) - Q aeration rate (volumetric gas flow rate per volume of medium, vvm) (min^–1) - N impeller speed (revolution per minute, rpm) (min^–1) - S substrate concentration (g l^–1) - S⁰ S at t_F=0 (g l^–1) - S₀ S in feed (g l^–1) - SR acid consumption (ml) - TDW total dry weight (g l^–1) - T temperature (° C) - t_F cultivation time (h) - U substrate conversion - X cell mass concentration (g l^–1) - Y_X/S vield coefficient - specific growth rate (h^–1) - _m maximum specific growth rate (h^–1)     

Kinetics of diffusion-coupled fermentation processes: The conversion of cellulose to protein

A combination of Fickian diffusion and Michaelis–Menten kinetics is proposed to describe the rate of diffusion-coupled biochemical reactions. This postulate leads to a nonlinear mathematical model which is solved by a perturbation technique. The result is a relation which permits identification of zones of relative diffusion or reaction influence. The conversion of cellulose to protein by Myrothecium verrucaria is a heterogeneous process that is well-suited to this type of analysis, although the data requirements are severe.     

A continuous thermophilic cellulose fermentation in an upflow reactor by aClostridium thermocellum-containing mixed culture

Summary A continuous thermophilic cellulose fermentation by aCl. thermocellum-containing mixed culture was carried out in an upflow reactor for a period of 100 days. The cellulose conversion rate was finally 0.35 g.1^–1.h^–1. Evidence that the fermentation process was influenced by both pH and dilution rate was given by the changes of concentration of the main fermentation products, acetic acid and ethanol. The role of cellodextrins and glucose as reactive intermediates in the process of cellulose breakdown was established.     

Conversion of a transmembrane to a water-soluble protein complex by a single point mutation

Proteins exist in one of two generally incompatible states: either membrane associated or soluble. Pore-forming proteins are exceptional because they are synthesized as a water-soluble molecule but end up being located in the membrane -- that is, they are nonconstitutive membrane proteins. Here we report the pronounced effect of the single point mutation Y221G of the pore-forming toxin aerolysin. This mutation blocks the hemolytic activity of the toxin but does not affect its initial structure, its ability to bind to cell-surface receptors or its capacity to form heptamers, which constitute the channel-forming unit. The overall structure of the Y221G protein as analyzed by cryo-negative staining EM and three-dimensional reconstruction is remarkably similar to that of the wild type heptamer. The mutant protein forms a mushroom-shaped complex whose stem domain is thought to be within the membrane in the wild type toxin. In contrast to the wild type heptamer, which is a hydrophobic complex, the Y221G heptamer is fully hydrophilic. This point mutation has, therefore, converted a normally membrane-embedded toxin into a soluble complex.     

Kinetic modelling of continuous submerged fermentation of cheese whey for single cell protein production

A mathematical model describing the kinetics of continuous production of single cell protein from cheese whey using Kluyveromyces fragilis was developed from the basic principles of mass balance. The model takes into account the substrate utilization for growth and maintenance and the effect of substrate concentration and cell death rate on the net cell growth and substrate utilization during the fermentation process. A lactose concentration below 1.91 g/L limited growth of yeast cells whereas a lactose concentration above 75 g/L inhibited the growth of the yeast. The model was tested using experimental data obtained from a continuous system operated at various retention times (12, 18 and 24 h), mixing speeds (200, 400 and 600 rpm) and air flow rates (1 and 3 vvm). The model was capable of predicting the effluent cell and substrate concentrations with R2 ranging from 0.95 to 0.99. The viable cell mass and lactose consumption ranged from 1.3 to 34.3 g/L and from 74.31% to 99.02%, respectively. A cell yield of 0.74 g cell/g lactose (close to the stoichiometric value of 0.79 g cell/g lactose) was achieved at the 12 h retention time-3 vvm air flow rate-600 rpm mixing speed combination. The total biomass output (viable and dead cells) at this combination was 37 g/L.     

Bioconversion of wheat stalk to hydrogen by dark fermentation: effect of different mixed microflora on hydrogen yield and cellulose solubilisation

This study determined hydrogen production, volatile fatty acids (VFAs) generation and cellulose solubilisation from anaerobic dark fermentation of wheat stalk and showed the effect of different mixed microflora. The cumulative hydrogen yields of anaerobic digested activated sludge (AS)-inoculated and anaerobic digested dairy manure (DM)-inoculated system were 23.3 and 37.0 mL/g VS at 204 h, respectively. A modified Gompertz equation was able to adequately describe the production of hydrogen from the batch fermentation by both mixed microflora. During the process, acetate and butyrate accounted for more than 76.1% of total VFAs for both fermentations. The extent of cellulose solubilisation approached 46.6% and 75.2% for AS- and DM-inoculated fermentation, respectively. The X-ray diffraction (XRD) showed that the crystallinities of both fermented stalks were partly disrupted by the mixed microflora, and DM-inoculated fermentation had more disruption than AS-inoculated one.     

Anaerobic degradation of cellulose by mixed culture

A mixed culture in which cellulose is capable of being converted to methane and carbon dioxide was obtained from an inoculum procured from a sewage-treatment plant and maintained in a synthetic medium containing tissue paper and an inorganic salt and vitamin mixture. The culture was tested for its ability to degrade 12 different paper and cotton products under batch conditions in 3-l anaerobic fermenters. This culture degraded 6-8 mmol/l per week of cellulose, expressed as glucose equivalents, with total gas yields of 0.3 m3/kg of cellulose degraded. The gas produced contained between 56 and 59% of methane. Maximum cellulose degradation occurred at chemical oxygen demand:nitrogen:phosphorus level of 80:5:1 and was adversely affected by high stirring rate. Also the presence of higher proportions of lignin in cellulose products adversely affected the ability of this culture to degrade cellulose.