培养条件对酪酸梭菌增殖生长的影响

主要探讨了培养基组分、培养时间、接种量、接种温度等条件下酪酸梭菌的生长及其芽孢的成熟转化状况,以期在提高菌体浓度及芽孢率的同时降低生产成本。实验结果表明,通过优化外源性碳氮源及比例和无机盐的使用量等培养条件得到的最佳培养基配方为:1.5%玉米粉,1%豆粉,0.4%K2HPO4,0.05%MgSO4,0.02%MnSO4,同时,以6%的接种量,在95℃热接种及初始pH为7.0的条件下,培养36h可获得较高的生物量。最终使酪酸梭菌活菌浓度提高到基础培养基的4.7倍,芽孢成熟转化率的提高率约为52%。      

青春双歧杆菌冻干保护剂筛选及高密度冻干工艺优化

为了探究青春双歧杆菌最适冻干保护剂配方,提高工业化生产效率,作者对不同糖与蛋白质类保护剂对双歧杆菌冻干保护特性、不同结构的糖类保护剂复配及其与蛋白质复配的保护效果进行研究,同时测定复合保护剂添加其他小分子物质对冻干存活率的影响,最后优化冻干前菌泥干物质与冻干保护剂的比例,以实现高密度冻干。研究结果表明,糖（醇）类保护剂对青春双歧杆菌的保护效果普遍高于蛋白类冻干保护剂,且四糖以下小分子糖的冻干保护效果较好,其中山梨糖醇和棉籽糖效果最优,二者复配（质量比1∶1）后冻干存活率提高到56%左右;将其与蛋白质、抗坏血酸、谷胱甘肽、微量元素等小分子复配,不会提高对菌体的冻干保护效果;考虑到实际应用,将山梨糖醇、棉籽糖与乳清蛋白以质量比3∶3∶2复配以提高菌粉的疏松度;菌泥与保护剂以干物质质量比1∶1.2混合,样品干物质总质量分数为25%时,青春双歧杆菌的冻干存活率达到（77.08±5.20）%。     

Modeling the relationship between microbial biomass and total viable count for a new bacterial isolate used in biodesulfurization of petroleum and its fractions

Microbial parameters in a biodesulfurization batch process are often needed to be defined as mass (mg/mL) rather than total viable count (cells/mL) or optical density. This study illustrates mathematical correlations between different techniques used for following up the growth of a new biodesulfurizing bacterial isolate.     

超声非热处理因素对细菌杀菌效果的影响

本文以大肠杆菌和金黄色葡萄球菌这两种食品中常见的污染菌为研究对象,考察了超声处理条件、介质、温度对超声非热杀菌效果的影响。结果表明:超声处理对大肠杆菌有较强的杀菌作用,金黄色葡萄球菌则对超声非热处理有很强的抵抗力;超声强度增大、作用时间延长、温度升高都有利于杀菌效果的提高;在培养基介质中的杀菌效果强于蒸馏水介质中的情况。结果分析认为,有利于空化作用提高或使细胞强度变弱的条件都有利于提高杀菌效果。冷藏结果表明,杀菌处理后的细菌没有出现复活生长的迹象。     

嗜酸乳杆菌的微胶囊化研究

研究了将益生菌、高效活菌保护剂和益生原一起作为核心物质,采用乳化法制备耐酸肠溶益生菌微胶囊的工艺过程。实验结果表明:加入40g/L玉米淀粉,150mL/L甘油,60g/L菊粉可显著提高微囊嗜酸乳杆菌冻干活菌数,其活菌数最高可达到2.2×1011,较之对照提高了近3个数量级。     

Campylobacter jejuni biofilm cells become viable but non-culturable (VBNC) in low nutrient conditions at 4 °C more quickly than their planktonic counterparts

Campylobacter jejuni remains the leading cause of foodborne disease in the developed world. In order to assess the ability of biofilm cells to enter and survive in a viable but non-culturable state, biofilm and planktonic cells of three strains of C. jejuni were incubated at 4 °C in phosphate buffered saline. Culturability was monitored by standard drop plating on Mueller Hinton agar and viability was measured using the LIVE/DEAD^® BacLight™ assay which assesses membrane integrity. Both biofilm and planktonic cells became non-culturable prior to becoming non-viable. Biofilm cells became non-culturable as early as 10 days for one strain, while planktonic cells became non-culturable after 30–40 days of treatment. Planktonic cells were still viable after 60 days of stress treatment. Biofilm cells showed significantly reduced viability by day 50 for the two clinical isolates and by day 60 for the poultry isolate. Of the media assessed for their ability to extend the culturability of the VBNC cells, Campylobacter Agar Base with the addition of Campylobacter Growth Supplement was most successful at prolonging culturability, but even with enrichment in Bolton broth, cells still remained viable and potentially infectious, longer than they were culturable.     

Warranty claim analysis considering human factors

Warranty claims are not always due to product failures. They can also be caused by two types of human factors. On the one hand, consumers might claim warranty due to misuse and/or failures caused by various human factors. Such claims might account for more than 10% of all reported claims. On the other hand, consumers might not be bothered to claim warranty for failed items that are still under warranty, or they may claim warranty after they have experienced several intermittent failures. These two types of human factors can affect warranty claim costs. However, research in this area has received rather little attention.In this paper, we propose three models to estimate the expected warranty cost when the two types of human factors are included. We consider two types of failures: intermittent and fatal failures, which might result in different claim patterns. Consumers might report claims after a fatal failure has occurred, and upon intermittent failures they might report claims after a number of failures have occurred. Numerical examples are given to validate the results derived.     

以果渣为基料的营养物对酵母菌MB生长的影响

以鲜果渣为基料,通过添加糖蜜、蔗糖、玉米粉等碳源,玉米浆、硫酸铵、乳清粉等氮源,白萝卜、芹菜、青椒等生长因子,进行单因素及正交试验并进行验证试验,研究对酵母菌MB菌株生长的影响,结果表明,添加糖蜜5%,玉米浆0.5%,白萝卜5%.活菌数可达1.22×108cfu/mL.由此可见,利用果渣培养酵母菌MB确实可行.     

Heat-killed lactic acid bacteria enhance immunomodulatory potential by skewing the immune response toward Th1 polarization

Abstract: Heat‐killed lactic acid bacteria not only possess immunomodulatory functions but also provide the advantages of longer product shelf life, easier storage, and more convenient transportation. To establish appropriate heat treatments for the industrial preparation of probiotics with immunomodulatory effects, 4 different heat treatments were used to kill 11 strains of lactic acid bacteria. Comparisons among the strains and with viable forms were carried out in terms of immunomodulatory activity and adhesion to Caco‐2 cells. Field‐emission scanning electron microscope (FE‐SEM) was employed to observe morphological changes in bacteria after heating. Among the 11 viable strains, Lactobacillus gasseri AI‐88 was the strongest inducer of interferon‐gamma (IFN)‐γ and interleukin (IL)‐12p70 production. However, after heat treatments its stimulatory ability was attenuated. Heat‐killed Enterococcus faecalis YM‐73 and Lactobacillus salivarius AP‐32 strains showed enhanced stimulation of IFN‐γ and IL‐12p70 secretion and coincidental decrease in IL‐13 production. The adhesion of lactic acid bacteria to Caco‐2 cells decreased with increases in temperature. However, heat exposure did not influence immunomodulatory activity. With rising temperature, roughness and unevenness of bacterial cell surfaces increased significantly. The results indicated that heat‐killed E. faecalis YM‐73 and L. salivarius AP‐32 have immunomodulatory ability via increased Th1‐associated cytokines and reduced Th2‐associated cytokines, switching the immune response from a Th2 toward a Th1 response. These 2 heat‐killed strains have the potential for development as commercial products.