A survey of the relationship between functional genes and acetaldehyde production characteristics in Streptococcus thermophilus by multilocus sequence typing

Streptococcus thermophilus is an important bacterium used in the production of fermented dairy products. Yogurt with good flavor is preferred by consumers; thus, variation in flavor-formation characteristics among isolates is attracting attention. Here, acetaldehyde production characteristics of 30 isolates were evaluated in parallel with genotyping and multilocus sequence typing of key functional genes involved in acetaldehyde production. The results showed that isolates could be divided into 3 phenotypically distinct groups: high-acetaldehyde-yielding isolates (>10 mg/L), medium-acetaldehyde-yielding isolates (5–10 mg/L) and low-acetaldehyde-yielding (<5 mg/L) based on evaluation of acetaldehyde production during yogurt storage. These groups, distinguishable by phenotypic characteristics, were clustered in corresponding groups based on functional gene multilocus sequence typing analysis. Combining functional gene sequence analysis of 30 Strep. thermophilus isolates with phenotypic evaluation of their flavor-related characteristics (specifically acetaldehyde production) demonstrated that groups of isolates established using genotype data analysis corresponded with groups identified based on their phenotypic traits. Interestingly, the 30 isolates of Strep. thermophilus showed significant phylogenetic clustering in acetaldehyde content by functional gene and acetaldehyde content analysis. A corresponding relationship exists between functional gene phylogenetic clustering and acetaldehyde content variation.     

Characterization and adsorption of a Lactobacillus plantarum virulent phage

Bacteriophage infection of lactic acid bacteria is considered one of the biggest worldwide problems in the food industry. Bacteriophages may cause negative effects on the fermentation of various dairy-based products. A virulent bacteriophage was isolated from an abnormal fermentation liquid of Lactobacillus plantarum IMAU10120. The characterization and influence of temperature, pH, divalent cations, and chloramphenicol on the adsorption ability of this phage were evaluated. The results showed that this phage belonged to the Siphoviridae family. It exhibited a burst time of 135 min and a burst size of approximately 215 counts expressed per milliliter per infective center. No significant effect was shown to influence its viability and adsorption at 10 to 37°C. More than 90% of phages exhibited infectivity from pH 5 to 9. Divalent ions and chloramphenicol did not have a significant influence on the adsorption of this phage. The information obtained in this study will enrich the database of lactobacilli virulent phages and provide a basis of information for the control of phages in the food fermentation industry.     

黑枸杞乳清酒发酵工艺优化及挥发性风味物质分析

采用单因素及正交试验对以乳清粉和黑枸杞为原料的黑枸杞乳清酒发酵工艺进行优化,并利用顶空固相微萃取-气相色谱-质谱联用技术（HS-SPME-GC-MS）分析黑枸杞乳清酒的挥发性风味成分。结果表明,黑枸杞乳清酒最佳发酵工艺为黑枸杞汁∶乳清液1∶3（V/V）、酵母接种量1.1%、发酵温度28 ℃、发酵时间115 h,此条件下所得黑枸杞乳清酒的感官评分为90.2分。在检测到的挥发性风味物质中,以酯类物质为主,占全部挥发性风味物质的72.42%,主要成分是癸酸乙酯和辛酸乙酯,其次是醇类物质,占检出总量的24.76%,主要成分是异戊醇和2-甲基丁醇,其他成分如酸类、醛类、烃类和酚类物质等检出含量很少,总占比只有2.82%。     

基于非标记蛋白质组学技术研究白羽肉鸡不同部位肌肉的蛋白差异

蛋白质作为肉类组成的重要部分,其发生改变会引起肉品质的变化,不同部位肌肉的理化特性及蛋白质组成不同。通过非标记蛋白质组学定量技术和数据非依赖型扫描技术,对白羽肉鸡鸡腿肉和鸡胸肉进行蛋白质鉴定和定量分析,并对其进行生物信息学分析。结果表明：鸡腿肉和鸡胸肉中共鉴定出875 个蛋白质与16 855 条肽段,且筛选出98 个差异蛋白;对鸡腿肉中的上调差异蛋白进行基因本体论（gene ontology,GO）组分富集分析的结果显示,在生物学过程中,其主要参与酰基辅酶A脱氢酶的脂肪酸β-氧化、三羧酸循环等过程,在细胞组分中主要富集于线粒体内,在分子功能中主要具有氧化还原酶活性、脂肪酰基辅酶A结合、烟酰胺腺嘌呤二核苷酸结合、肌动活动、电子载体活性、黄素腺嘌呤二核苷酸结合和催化活性等功能;鸡胸肉中上调差异蛋白的GO组分富集分析结果显示,在生物学过程中,其主要富集在骨骼肌收缩过程,在细胞组分中富集于胞外外泌体中的蛋白质最多;鸡腿肉中的高表达蛋白均富集于运动相关功能,而鸡胸肉中的上调蛋白多富集于肌肉收缩功能。     

基于非标记蛋白质组学技术筛选影响察哈尔羊肌肉品质的重要分子标记

为研究察哈尔羊不同部位肌肉蛋白质组成差异及差异蛋白功能,通过数据信息依赖性获取与SWATH非标记蛋白组学定量技术,对察哈尔羊背最长肌和臀肌进行蛋白质鉴定和定量分析,并对其进行生物信息学分析。结果表明：察哈尔羊背最长肌和臀肌肌肉中共检测到蛋白质1 073 个,筛选出差异蛋白140 个,其中背最长肌中高表达差异蛋白116 个,低表达差异蛋白24 个;背最长肌中高表达差异蛋白GO（gene ontology）功能富集分析结果表明,在细胞组分中,富集于细胞外外泌体中的蛋白质最多,其次富集于细胞膜内,在分子功能中,蛋白质主要参与分子内转移酶活性、聚RNA结合和L-乳酸脱氢酶活性过程,在生物学进程中,蛋白质主要参与碳水化合物代谢过程、肌节组织和肌肉收缩过程;通过差异蛋白的网络互作分析发现,肌纤维组成模块包括肌球蛋白-11、肌球蛋白-1（myosin-1,MYH1）、肌间蛋白-1、肌球蛋白-2（myosin-2,MYH2）、肌球蛋白-8（myosin-8,MYH8）、肌球蛋白轻链激酶-2、肌球蛋白轻链-2、肌钙蛋白T-3、视松蛋白和肌球蛋白结合蛋白C等蛋白质,肌球蛋白MYH1、MYH2、MYH8有望成为影响肉品质的重要分子标记。     

微生物与肉类腐败变质

本文介绍了腐败肉的特征、分类以及引起肉类腐败变质的原因与条件,其中以微生物引起的腐败最为普遍,因此,本文重点介绍了导致肉类腐败变质的微生物的种类及特性,以及如何防止肉的腐败变质。     

红枣醋发酵过程中醋酸发酵条件的优化

旨在采用液态静止表面发酵法,通过正交实验对红枣醋的醋酸发酵过程进行优化。得出醋酸发酵的最佳条件为温度32℃、酒精度6%、接种量10%、初始pH4.4,醋酸发酵结束后各项指标均符合国家食醋卫生标准,且红枣醋的Vc含量明显高于其他类型的果醋。     

光源和光照度对UHT奶脂氧化程度和感官品质的影响

为找到UHT奶贮存期内脂氧化程度和感官品质影响较小的光源及光照度范围,为UHT奶的合理贮存、流通条件的确定提供依据,研究在(23±1)℃贮存条件下,采用避光、白炽灯和日光灯进行不同光源照明实验,并在60～2000lx光照度范围内设置6种处理,进行不同光照度实验。结果表明,在(23±1)℃贮存条件时,日光灯照射对UHT奶脂肪氧化程度和感官品质的影响远大于白炽灯。同时在(23±1)℃下贮存时,采用日光灯照射其光照强度应低于950lx。     

自然发酵乳中粪肠球菌和屎肠球菌的4种鉴定方法的比较

采用传统生理生化鉴定方法,16S rRNA基因序列分析技术,16S-23S rRNA间区序列多态性分析技术,变性梯度凝胶电泳技术(DGGE),对分离于自然发酵乳中的9株粪肠球菌和6株屎肠球菌进行鉴定,并对4种鉴定方法进行比较和评价。结果表明,16S-23S rRNA间区序列多态性分析技术和DGGE技术不但可以快速、精确地区分粪肠球菌和屎肠球菌,而且能够将粪肠球菌和屎肠球菌种内的不同基因亚型区分开,而传统生理生化鉴定方法和16S rRNA基因序列分析技术较以上两种方法区分效果略差。     

马奶酒中抗单增李斯特氏菌细菌素产生菌的筛选及鉴定

从内蒙古传统乳制品酸马奶酒中分离出144株乳酸菌,通过双层琼脂平板扩散法筛选出具有明显抑菌作用的菌株.在排除有机酸、H2O2等的干扰后,其中1株乳酸菌的发酵上清液对受试的单核细胞增生李斯特氏菌表现出明显抑制作用;进一步硫酸铵沉淀、透析及浓缩处理后,其抑菌活性显著增强,说明其代谢产物中含有蛋白质类抑菌物质,可能是细菌素.经生理、生化试验和形态学观察,将该菌株鉴定为屎肠球菌(Enterococcus faecium).