多糖的研究进展

对多糖的分离纯化、结构分析、药理活性及发酵调控进行了综述。  

Effect of benzoic acid on metabolic fluxes in yeasts: a continuous-culture study on the regulation of respiration and alcoholic fermentation.

Addition of benzoate to the medium reservoir of glucose-limited chemostat cultures of Saccharomyces cerevisiae CBS 8066 growing at a dilution rate (D) of 0.10 h-1 resulted in a decrease in the biomass yield, and an increase in the specific oxygen uptake rate (qO2) from 2.5 to as high as 19.5 mmol g-1 h-1. Above a critical concentration, the presence of benzoate led to alcoholic fermentation and a reduction in qO2 to 13 mmol g-1 h-1. The stimulatory effect of benzoate on respiration was dependent on the dilution rate: at high dilution rates respiration was not enhanced by benzoate. Cells could only gradually adapt to growth in the presence of benzoate: a pulse of benzoate given directly to the culture resulted in wash-out. As the presence of benzoate in cultures growing at low dilution rates resulted in large changes in the catabolic glucose flux, it was of interest to study the effect of benzoate on the residual glucose concentration in the fermenter as well as on the level of some selected enzymes. At D = 0.10 h-1, the residual glucose concentration increased proportionally with increasing benzoate concentration. This suggests that modulation of the glucose flux mainly occurs via a change in the extracellular glucose concentration rather than by synthesis of an additional amount of carriers. Also various intracellular enzyme levels were not positively correlated with the rate of respiration. A notable exception was citrate synthase: its level increased with increasing respiration rate. Growth of S. cerevisiae in ethanol-limited cultures in the presence of benzoate also led to very high qO2 levels of 19-21 mmol g-1 h-1. During growth on glucose as well as on ethanol, the presence of benzoate coincided with an increase in the mitochondrial volume up to one quarter of the total cellular volume. Also with the Crabtree-negative yeasts Candida utilis, Kluyveromyces marxianus and Hansenula polymorpha, growth in the presence of benzoate resulted in an increase in qO2 and, at high concentrations of benzoate, in aerobic fermentation. In contrast to S. cerevisiae, the highest qO2 of these yeasts when growing at D = 0.10 h-1 in the presence of benzoate was equal to, or lower than the qO2 attainable at mu(max) without benzoate. Enzyme activities that were repressed by glucose in S. cerevisiae also declined in K. marxianus when the glucose flux was increased by the presence of benzoate.(ABSTRACT TRUNCATED AT 400 WORDS)  

胞外纤溶酶产生菌的筛选及其产酶条件研究

从豆豉、酱豆和纳豆样品中分离筛选到一株具强力纤溶活性的细菌 ,编号为NK—5,经鉴定为芽孢杆菌属枯草杆菌群细菌。该菌在固态基质及液体培养基中均产生大量胞外纤溶酶。摇瓶发酵试验表明 ,其最适产酶碳源和氮源分别为蔗糖和蛋白胨。通过正交试验确定最适产酶培养基为 :豆粕粉 2 0 %、麸皮 0 5%、玉米淀粉 0 5%、KH2 PO4 0 2 %、K2 HPO40 4 %、MgSO4 0 0 5%、CaCl2 0 0 2 % ,pH7 0。在优化条件下 ,发酵液酶活达 6 83 3IU/mL  

发酵大豆制品中异黄酮形成及其功能

大豆中异黄酮主要同葡萄糖以β-糖苷键的形式形成糖甙，大豆及豆粕经过产β-葡萄糖苷酶的微生物发酵，形成大豆异黄酮，目前已从大豆发酵制品中分离出15种异黄酮，其中主要是梁料木素、大豆甙元和6，7，4-三羟基异黄酮，异黄酮不仅是豆科类主要色素，而且具有预防心血管性疾病、抗癌和肿瘤效应及抗氧化性等多种生物学活性。  

微生物发酵豆粕营养特性研究

通过枯草芽孢杆菌（Bacillus subtilis）、酿酒酵母菌（Saccharomyces cerevisiae）、乳酸菌（Lactobacillus）对豆粕进行发酵，并对发酵后豆粕的营养特性进行分析，对比了微生物发酵前后豆粕营养成分的变化。结果表明：发酵后豆粕中粗蛋白的含量比发酵前提高了13．48％（P〈0．01），粗脂肪的含量比发酵前提高了18．18％（P〈0．01），磷的含量比发酵前提高了55．56％（P〈0．01），氨基酸的含量比发酵前提高了11．49％，钙的含量稍有降低，差异不显著。其中胰蛋白酶抑制因子和豆粕中的其他抗营养因子得到了彻底消除。发酵后豆粕中高分子蛋白含量比发酵前下降了75．57％，中分子蛋白含量较发酵前降低了86．77％，低分子蛋白含量比发酵前提高了2．25倍。微生物发酵使豆粕本身蛋白质发生一定程度的分解，从而获得了一种更优质的蛋白饲料。  

大白菜发酵过程中亚硝酸盐消长规律的研究

对大白菜在发酵过程中亚硝酸盐的形成规律进行了研究。结果发现 ,亚硝酸盐的出现期主要集中在发酵前期 ,随发酵液酸度的增加亚硝酸盐逐渐消失。亚硝峰的形成主要是由杂菌将硝酸盐还原为亚硝酸盐的作用 ,与大白菜体内硝酸还原酶无直接关系。亚硝峰消失的原因一是在酸性条件下的化学降解 ,二是乳酸菌对亚硝酸盐的还原作用。纯接种发酵可降低亚硝峰 ,无论是接入单一菌株还是接入混合菌株都能明显地降低亚硝峰 ,尤以混合接种效果最佳  

酸奶发酵机理及后酸化控制措施

介绍了酸奶发酵过程中 ,乳酸菌代谢乳糖的机理及发生的各种生理生化反应。酸奶在储藏过程中 ,会发生后酸化。基于以上机理 ,重点介绍了防止酸奶后酸化的措施  

以基因重组技术开发木聚糖类半纤维素资源

木聚糖类半纤维素是一类取之不尽而又亟待开发利用的碳水化合物，经生物降解后所产生的木糖和少量其它单糖，可以用作基本碳源生产各种发酵产品，包括有机酸、氨基酸、单细胞蛋白、糖醇、工业酶类、溶剂或燃料醇。有关半纤维素酶及其基因的研究已经积累了很多资料，其中包括木聚糖酶、木糖苷酶、阿拉伯糖苷酶、葡萄糖醛酸酶、木聚糖乙酰酯酶以及它们的基因。通过基因重组技术可以使发酵工程菌获得降解半纤维素的能力，或者把能有效降解半纤维素的微生物构建成发酵工程菌，从而把半纤维素转化为所需求的生物工程产品。  

荔枝酒发酵工艺研究

研究了荔枝酒发酵的关键技术。结果表明 ,荔枝取汁时加入 3 0 0mg偏重亚硫酸钾 /kg果肉 ,将果汁调整至pH4 0 ,可溶性固形物 2 5% ,接入扩大倍数为 11的经驯化的葡萄酒活性干酵母 ,于 2 0℃进行发酵 ,可酿出具有荔枝果香和醇香的干白荔枝酒  

烤烟自然醇化与人工发酵过程中微生物变化及其与酶活性关系的研究

对自然醇化与人工发酵过程中烤烟微生物数量变化、酶活性(α-淀粉酶、蛋白酶、多酚氧化酶、琥珀酸脱氢酶、脂氧合酶、苯丙氨酸氨裂解酶)变化及两者间的相关性进行了研究.结果表明,烤烟中芽孢杆菌属(Bacillus)和梭菌属(Clostridium)细菌为优势种群.在自然醇化与人工发醇过程中,微生物总数均呈现出下降趋势,但不同微生物种群在不同发酵过程中数量的变化有明显差异,不同的酶在不同发酵过程中的活性变化也存在明显差异.微生物数量与酶活性间存在明显相关关系,但在不同的发酵过程中,不同的微生物对不同种类酶活性的影响不同.