Effect of salt reduction on nutritional,functional and sensory aspects of Anhui‑style doubanjiang,a traditional Chinese broad bean paste

This study aimed to reveal the effect of salt reduction on the nutritional,functional and sensory aspects of doubanjiang through preparing three sets of doubanjiang fermentation(Sample H,Sample M and Sample L)with different salt concentrations.The results showed that fermentation with lower salt concentration led to significantly higher amino acids concentrations in doubanjiang,while the organic acids concentrations were also slightly increased.For biologically active compounds,the concentrations of total flavonoids,total phenols and five monomer isoflavones in Sample L were all significantly higher than those in Sample M and Sample H.Moreover,better anti-oxidant ability was observed in doubanjiang samples fermented with lower salt concentration.Bacillus and Millerozyma genus were found to be closely related to the formation of amino acids and biologically active compounds in doubanjiang,while organic acids were highly correlated with Cronobacter,Erwinia,Trabulsiella,Enterobacter and Millerozyma genus.Through sensory evaluation and electric tongue,unsatisfactory sensory characteristics,such as lighter color,strong acid taste and off-flavor,were found in lower salt fermented doubanjiang samples.This indicated that lower salt concentration favored the nutrition and function of doubanjiang while negatively influenced doubanjiang flavor.This study deepened our understanding of the roles of salt concentration on doubanjiang fermentation and provided guidance for the further development of low-salt doubanjiang.

Lager啤酒酵母RLM1基因调控对其抗自溶性能的影响

啤酒酵母的自溶会严重影响啤酒的品质,而酵母的质量也被认为是啤酒酿造的关键因素之一。前期在啤酒酵母自溶的研究中发现细胞完整性途径中重要的转录因子RLM1基因与酵母自溶有密切关系。本研究在啤酒酵母单倍体菌株中对RLM1进行敲除与过表达,发现RLM1敲除后,酵母菌抗自溶性能差,而RLM1过表达则有助于酵母的抗自溶。另外,发现RLM1基因的敲除影响了酵母的抗渗透压性能、细胞壁损伤的耐受性、抗氮饥饿性能和温度耐受性。研究发现细胞壁组装及DNA损伤应答相关基因GAS1的表达随RLM1的过表达与敲除而调整,而CWI途径中其他相关基因的调控方式并没有明显的规律,推测RLM1可能主要影响了CWI途径中GAS1基因的表达,进而提高啤酒酵母在恶劣环境中的抗逆性。此研究结果对于进一步选育抗自溶啤酒酵母以及了解啤酒酵母的自溶机制提供了基础。

微生物1,3-1,4-β-葡聚糖酶蛋白质改造及工业应用研究进展

1,3-1,4-β-葡聚糖酶(E.C.3.2.1.73)是一种重要的工业用酶,其可以通过特异性切割毗邻β-1,3-糖苷键的β-1,4-糖苷键将β-葡聚糖或地衣多糖降解为纤维三糖和纤维四糖。微生物β-葡聚糖酶属于糖苷水解酶家族16,其三维结构为卷心蛋糕状的逆向β-片层结构。文中综述了近些年来β-葡聚糖酶在工业上的应用情况及酶蛋白质工程改造的研究进展,并对其研究前景进行了展望。

啤酒酵母细胞壁环境压力应答机制研究进展

酵母细胞壁在细胞形态学的建立和维持中起重要作用,有助于细胞抵御环境变化。细胞壁主要由β-葡聚糖、甘露糖蛋白和几丁质组成,其组成和结构会由于压力胁迫发生动态重构。同时为了适应环境压力变化,啤酒酵母细胞壁在长期驯化过程中表现出相关压力应答机制。文中介绍了啤酒酵母细胞壁组成与结构,并综述了细胞壁重构与信号通路调控的分子机制。

传统豆瓣酱微生物群落发酵演替规律及其功能分析

【目的】解析中国传统豆瓣酱发酵过程中的微生物群落演替规律和理化代谢物质变化,探讨不同发酵阶段影响豆瓣酱风味的核心功能微生物。【方法】采用高通量测序解析豆瓣酱发酵过程中的微生物群落结构和演替,并跟踪检测发酵过程中的理化代谢物质,然后分析微生物群落和理化代谢物质变化之间的相关性,最后在体外分离核心微生物并对其功能特性进行验证。【结果】细菌和真菌群落结构在发酵前期显著变化,并在中后期逐渐趋于稳定。优势细菌主要是Staphylococcus、Bacillus和Weisiella,其中Staphylococcus在整个发酵过程中呈上升趋势,而Bacillus和Weisiella呈下降趋势。真菌群落结构较为简单且稳定,其中Aspergillus在整个发酵过程中的平均丰度占真菌总群落的97%以上,Zygosaccharomyces呈先上升后下降的趋势。相关性分析和体外功能验证表明,功能微生物(Aspergillus oryzae、Bacillus subtilis、Staphylococcus gallinarum、Weisiella confusa和Zygosaccharomyces rouxii)在不同发酵阶段发挥着不同的关键作用。【结论】在成曲和发酵前期Aspergillus oryzae、Bacillus subtilis分泌各种酶来降解大分子物质,Aspergillus oryzae、Staphylococcus gallinarum和Weisiella confusa导致了酱醅的酸化和氨基酸的生成,而耐盐的Zygosaccharomyces rouxii在发酵中后期对风味物质的形成起重要作用。

RIM21基因缺失对拉格啤酒酵母絮凝性能的影响

拉格啤酒酵母是我国啤酒酿造的主要菌种。细胞絮凝是啤酒酵母重要的生产性状,在不影响发酵性能的情况下适度提高酵母的絮凝能力,有助于发酵结束时细胞和产物的分离,有利于工业化啤酒生产,具有较高的经济价值。前期在对一株工业用拉格啤酒酵母G03及其絮凝突变株的研究中,挖掘到一个可能影响啤酒酵母絮凝性的候选基因RIM21。为了验证该基因的作用,文中在G03中对RIM21进行了敲除,发现RIM21敲除后,酵母在11℃发酵条件下的絮凝性能增强,基因FLO5、Lg-FLO1及细胞壁完整性途径中的部分基因表达上调。同时,CO2失重、酒精度、发酵度等发酵指标未有明显变化。另外,发现RIM21的缺失增强了啤酒酵母对细胞壁抑制剂的耐性。研究结果为阐释低温发酵条件下啤酒酵母的絮凝调控机理及菌株絮凝性的改善提供了基础。

Metabolic energy variation of yeast affects its antioxidant properties in beer brewing

Oxidation destroys the flavor and freshness of the beer,and yeast with improved antioxidant activity would benefit the flavor stability of the beer.The aim of this work was to study the antioxidant networks of lager yeast for brewing industry.Through transcriptome and metabolome analysis,we were able to map changes in anti-oxidant pathways and transcription of genes in lager yeast.Results suggested that metabolic energy variation in yeast might be the main reason for the improved anti-oxidant capacity.Lower metabolic rate kept the yeast at relatively lower respiratory status at the end of fermentation,thereby prolonging the lifespan and potentially supporting its usage in serial fermentations.Up-regulation of mannose synthesis and hexose transport strengthened the cell structure,which may have contributed to the anti-oxidant capacity of yeast.A deeper understanding of the globally regulation pattern of anti-oxidation in lager yeast is expected to support the design of strain development strategies for improved anti-oxidant capacity of yeast for fermentation industry.

Screening of strains with potential hypoglycemic effect and its application in fermented garlic production

Microbial fermentation could produce many active substances in green and pollution-free ways.In recent years,studies on the hypoglycemic ability of microorganisms had become a trending topic in the prevention and treatment of diabetes.Garlic is a food containing a variety of biologically active substances and physiological functions,but it is not accepted by the general public because of its strong pungent smell.In our study,the microorganisms with potential hypoglycemic effect were screened from strains resistant to garlic juice.As a result,41 strains of Bacillus,157 strains of lactic acid bacteria,and 23 strains of yeast with tolerance of garlic juice were screened from the selected 568 strains.After primary screening ofα-amylase inhibitor,it was found that 15 Bacillus and 9 lactic acid bacteria had highα-amylase inhibitory activity.Besides,afterα-glucosidase inhibitor re-screening,Pediococcus acidilactici Z1 with highα-amylase inhibitory activity andα-glucosidase inhibitory activity was screened out.The results of fermented garlic showed that the inhibition rate ofα-amylase andα-glucosidase of garlic from different origins were significantly increased from 59.09 to 63.99%(p<0.01)and from 52.71 to 71.93%(p<0.01)after Z1 fermentation,respectively.The improvement rates ofα-amylase andα-glucosidase were 107.69 to 287.32%,and 197.74 to 239.86%,respectively.In a word,this study provides a theoretical and experimental basis for the development of new functional garlic products.