微生物发泡剂发泡机制及在泡沫混凝土中的应用

以酵母菌为原材料制备微生物发泡剂,揭示微生物发泡剂的发泡机制,并针对不同发泡机制,分别采用混合搅拌法和预制泡混合法制备泡沫混凝土,研究了混泡工艺对泡沫混凝土物理力学性能和微观结构的影响.结果表明:微生物发泡剂既可以利用酵母菌的发酵作用产生CO2形成泡沫,还可以利用酵母菌的自身生化反应降低发泡剂溶液的表面张力,在外力作用...     

啤酒酵母RNA提取条件的优化及其磁性固定化

通过浓盐法对啤酒酵母RNA进行提取,以磁性壳聚糖微球为载体,戊二醛交联法对RNA进行磁性固定化。通过比较反应体系中的无机磷和总磷的质量分数,对RNA的提取条件和固定化条件进行优化。结果表明,RNA提取温度对提取率的影响最为显著;在提取时间4h、提取温度100℃、氯化钠质量分数为10%和酵母质量分数为8%的最优条件下,RNA提取率达到6.13%。戊二醛交联法磁性固定化RNA的最佳条件为:反应时间4h,温度40℃;RNA最佳添加量为30mL(质量浓度2mg/mL)。     

利用酵母菌处理木糖厂生产废水营养条件研究

利用酵母菌处理木糖厂生产废水既能回收菌体又能去除废水中部分COD,是一种处理废水经济有效的方法。但废水COD浓度高,其它营养物相对不足,酵母菌生长缓慢,影响废水的处理效率。通过双质量指标的正交实验探索了利用酵母菌处理废水的氮源、磷源和酵母膏三种营养物质的最佳加入量。结果表明最佳营养条件加入量为：0．3％的尿素＋0．4％的磷酸盐＋0．3％的酵母膏,此条件下的最优工程平均为μCOD=48.1,μ菌＝18．8,对于质量指标1和质量指标2试验真值的95％置信区间分别为（47．2,49）和（18．2,19．4）。     

Reduced acetaldehyde production by genome shuffling of an industrial brewing yeast strain

High levels of acetaldehyde produced by yeast during fermentation can be of concern to product quality. A novel approach, based on genome shuffling, was applied to reduce the production of acetaldehyde by industrial brewing strain YS86. Four isolates with different impacts of acetaldehyde concentration were obtained from populations generated by ultraviolet irradiation and nitrosoguanidine mutagenesis. These yeast strains were then subjected to recursive pool‐wise protoplast fusion. A strain library that was likely to yield positive colonies was created by fusing the lethal protoplasts obtained from both UV irradiation and heat treatments. After two rounds of genome shuffling, a recombinant YSF2–9 strain produced less acetaldehyde than wild‐type strain YS86, by 64.5 and 66.2% in laboratory and pilot plant fermentations, respectively. The shuffled yeast strain YSF2–9 was genetically stable and may have a potential application in brewing industry for managing acetaldehyde in beer. Copyright © 2017 The Institute of Brewing & Distilling     

富铁面包酵母的筛选及富集条件研究

本文探索获得富铁面包酵母的富集条件。筛选获得一株富铁能力较强的面包酵母菌株QN006。通过单因素实验确定该菌株富铁工艺条件为:铁盐种类为硫酸亚铁,亚铁离子浓度为900μg/mL,添加时间为0h,温度为28℃,pH为5.0。在此条件测得面包酵母QN006的铁富集量为13.92mg/g干菌体,不加糖面团发酵力达到623mL/h。     

Incidence of citrinin in red yeast rice and various commercial Monascus products in Taiwan from 2009 to 2012

Red yeast rice, produced by the fermentation of red yeast (Monascus purpureus) with white rice, has long been used in food colouring and meat preservation in Asia. Recently, powdered red yeast rice and its formulated products, used worldwide as dietary supplements, have the ability of reducing blood-lipid levels in humans. However, some Monascus strains could produce the mycotoxin citrinin as a secondary toxic metabolite so that commercial Monascus products are of a serious concern to the public now. The aim of this study was to obtain information about the occurrence of citrinin in red yeast rice and various commercial Monascus products in Taiwan from 2009 to 2012. A simple and rapid HPLC-fluorescence method was developed to detect citrinin in red yeast rice and Monascus products. The method's performance was acceptable in terms of recoveries, which ranged from 81.2% to 94.3% for citrinin-spiked samples at levels of 0.1, 1 and 10 mg/kg, and the relative standard deviation ranged from 2.5% to 5.7%. The limit of quantification of 0.05 mg/kg was achieved. The survey results showed that among total 302 samples, the incidences of citrinin contamination were 69.0%, 35.1% and 5.7% for red yeast rice (raw material), dietary supplements and red yeast rice processed products, respectively. The mean contamination levels were 13.3, 1.2 and 0.1 mg/kg for red yeast rice (raw material), dietary supplements and red yeast rice processed products, respectively. Such high citrinin contamination rate and level is worthy of note.     

Effects of high solid concentrations on the efficacy of enzymatic hydrolysis of yeast cells and the taste characteristics of the resulting hydrolysates

Effects of solid concentrations on enzymatic hydrolysis of yeast cells and the taste characteristics of the resulting hydrolysates were examined. Results showed that increased solid concentrations ranging from 10% to 30% resulted in a mild increase in degree of hydrolysis (DH) of hydrolysates during the whole hydrolysis process, whereas an obvious inhibition effect on DH was found at hydrolysates with 40% of solid concentration. The levels of amino nitrogen and total nitrogen of supernatant with 40% of solid concentration were six‐fold higher than those of hydrolysates with 10% of solid concentration at all hydrolysis time. After 21 h of hydrolysis, there was no significant difference in molecular weight distributions of hydrolysates with different solid concentrations, while a significant increase in amino acid contents of hydrolysates with high solid concentrations was found. Results from sensory evaluation showed that the intensities of umami, mouthfulness and continuity in umami solution could be significantly improved by supplementing with the resulting hydrolysates with high solid concentrations.     

高活性干酵母生产的干燥设备和工艺介绍

采用流化床快速干燥工艺进行高活性干酵母的生产,产品水分含量从67%干燥到5%,参数控制准确,活性保持良好。系统配套CIP和自动化控制,减少人工干预,保证工艺稳定。