Effects of Aspergillus spp. exogenous fibrolytic enzymes on in vitro fermentation of tropical forages

BACKGROUND: Cellulose and hemicellulose are quantitatively the most important structural carbohydrates present in ruminant diets. Rumen micro‐organisms produce enzymes that catalyse their hydrolysis, but the complex network formed by structural carbohydrates and lignin reduces their digestibility and restricts efficient utilisation of feeds by ruminants. This study aimed to produce two enzymatic extracts, apply them in ruminant diets to determine the best levels for ruminal digestibility and evaluate their effects on in vitro digestibility. RESULTS: In experiment 1 a two‐stage in vitro technique was used to examine the effects of different enzymatic levels of Aspergillus japonicus and Aspergillus terricola on tropical forages. Enzyme addition had minor effects on corn silage at the highest enzymatic level. In experiment 2 an in vitro gas production (GP) technique was applied to determine apparent in vitro organic matter digestibility and metabolisable energy. The addition of enzymes in GP showed interesting results. Good data were obtained using sugar cane and Tifton‐85 hay supplemented with extracts of A. japonicus and A. terricola respectively. CONCLUSION: Overall, the study suggests that addition of crude extracts containing exogenous fibrolytic enzymes to ruminant diets enhances the effective utilisation of ruminant feedstuffs such as forages. Copyright © 2012 Society of Chemical Industry     

根霉菌在食品工业中应用的安全性

一些根霉菌种产生毒素使其在发酵食品中的应用安全性受到了质疑.该文从毒素的研究进展和现状出发提出根霉菌可能存在的食品安全问题,并介绍文献资料在毒素研究过程中采用的一些新方法,希望从食品安全角度研究根霉菌的科学应用问题,为我国合理利用根霉菌发酵生产安全的发酵食品奠定基础.     

包装饮用水中铜绿假单胞菌实时荧光定量PCR快速检测

目的:有效弥补传统微生物学检验方法的缺陷。方法:针对GB 8538—2022中铜绿假单胞菌的毒力基因pcrL和16S rRNA基因的V3～V4区保守序列设计合成引物和探针,建立实时荧光PCR方法。结果:该方法可以有效扩增常见标准储备菌株的16S rRNA基因,且对铜绿假单胞菌标准储备菌株的毒力基因pcrL的检测效果良好,观察到明显的“S”型扩增曲线,但对常见的食源性致病菌无扩增曲线。当菌液浓度<10 CFU/mL时,pcrL基因仍有扩增曲线,其检测范围为10～10⁷ CFU/mL,检测限为10 CFU/mL;不同菌液浓度下毒力基因pcrL的Ct平均值为18.0～38.6。对近3年湖南省14个县、市抽查检验(瓶)桶装水中铜绿假单胞菌不合格样品进行进一步检测,符合率达到100%。结论:该方法对铜绿假单胞菌携带毒力因子pcrL检测的灵敏度较高;且操作简便、特异性强,具有良好的实用性。     

基于高通量测序技术的蓝莓果实中细菌和真菌菌群多样性分析研究

目的 分析蓝莓中细菌和真菌菌群的组成及其多样性,探究不同蓝莓样品中微生物的暴露水平。方法 构建了蓝莓中微生物菌群的基因组文库,利用高通量测序技术分析了5种蓝莓中细菌和真菌菌群的组成及其多样性,借助微生物属水平和种水平分析比较了蓝莓中细菌和真菌菌群组成和丰度信息。结果 5种蓝莓中微生物菌群的多样性较高,但其细菌和真菌菌群组成仍存在共有特征,细菌和真菌中共有的操作分类单元数量分别为76和42。蓝莓中优势细菌主要归属于放线菌门、拟杆菌门、蓝藻菌门、厚壁菌门和变形菌门,优势真菌主要归属于子囊菌门、担子菌门和被孢霉门。结论 不同蓝莓样品中微生物菌群的组成变化较大,真菌菌群的多样性比细菌更丰富,这对蓝莓的腐烂变质、贮藏保鲜和生物防控研究具有重要意义。     

黑龙江省烟草野火病菌生理小种鉴别寄主的筛选

为明确黑龙江省烟草野火病菌生理小种的分化情况,采用针刺接种法,将黑龙江省主要烟区采集的15个烟草野火病菌菌株接种到28个供试烟草品种上,通过对发病率的差异性分析和聚类分析来测定供试烟草品种的抗性表现,从而建立了一套鉴定烟草野火病菌生理小种的鉴别寄主体系,并将15个供试菌株划分为Ⅰ,Ⅱ,Ⅲ,Ⅳ4个生理小种.     

阪崎肠杆菌(克罗诺杆菌属)分子检测方法研究进展

阪崎肠杆菌(现克罗诺杆菌属)是一种重要的食源性条件致病菌,因其能通过污染婴幼儿配方食品导致严重的新生儿脑膜炎、菌血症和小肠结肠炎等疾病,而受到广泛的关注。其分子生物学检测方法克服了传统检测方法实验操作繁琐、耗时长等问题。目前常用的分子生物学方法主要有普通PCR、实时荧光定量PCR、环介导恒温扩增、探针方法等。     

食品中荧光假单胞菌聚合酶链式反应检测体系的建立和评价

建立用聚合酶链式反应(polymerase chain reaction,PCR)检测食品中荧光假单胞菌的方法。分别针对16～23S rRNA基因间隔区序列、gyrB基因以及通过生物信息学方法发掘到的4个种特异性基因设计6对检测引物,通过初步特异性实验,筛选出一对种特异性最佳的引物。最终建立以gyrB基因为检测靶点的PCR扩增体系,并对体系进行系统评价。结果表明:该方法可特异检测荧光假单胞菌的存在,纯DNA检测灵敏度为14.9fg/μL(2～3拷贝/μL),纯培养物检测灵敏度为2.8×102CFU/mL。豆奶样品经15h充分增菌可提高检测灵敏度至0.28CFU/25g。     

Detection of Brettanomyces spp. in Red Wines Using Real-Time PCR

The question if the "Brett character" is a favorable wine attribute is one of the most controversial issues and it is currently addressed by many researches. Actually, the presence of Brettanomyces/Dekkera in wine during barrel aging is often associated to detrimental organoleptic characteristics depending on the release of volatile phenols (for example, 4-ethylphenol and 4-ethylguaiacol); for that reason the possibility to rapidly detect the yeast at the early stage of wine production could allow preventive actions to reduce wine spoilage. In this work, 25 and 5 samples from conventional and organic vineyards, respectively, all suspected to be spoiled by Brettanomyces/Dekkera spp., were analyzed using both culture-dependent and culture-independent techniques. In particular, a DNA extraction protocol and a real-time quantitative PCR (qPCR) assay to directly detect and quantify B. bruxellensis were optimized. Results showed that B. bruxellensis was present in 22 of 30 samples, ranging from 10 to 10(4) CFU/mL, lower values being found in organic wines (10 to 10(2) CFU/mL). Overall, qPCR was proved to be a useful and valuable wine control system, since 12 samples were recorded as positive for yeast presence when analyzed by qPCR and negative in case of plate count analyses. Practical Application: Brettanomyces cells were detected using a qPCR method, optimized in this study, which allows to obtain results quickly.     

Composition and health effects of phenolic compounds in hawthorn (Crataegus spp.) of different origins

Epicatechin, aglycons and glycosides of B-type oligomeric procyanidins and flavonols, phenolic acids and C-glycosyl flavones are the major groups of phenolic compounds in hawthorn (Crataegus spp). The total content of phenolic compounds is higher in the leaves and flowers than in the fruits. Procyanidins dominate in the fruits, whereas flavonol glycosides and C-glycosyl flavones are most abundant in the leaves. Genotype and developmental/ripening stage have strong impacts. Procyanidin glycosides and C-glycosyl flavones may be chemotaxonomic markers differentiating species and varieties of hawthorn. Future research shall improve the separation, identification and quantification of procyanidins with degree of polymerisation (DP) ≥ 6, procyanidin glycosides, C-glycosyl flavones and some flavonol glycosides. In vitro and animal studies have shown cardioprotective, hypolipidaemic, hypotensive, antioxidant, radical-scavenging and anti-inflammatory potentials of hawthorn extracts, suggesting different phenolic compounds as the major bioactive components. However, the varying and insufficiently defined composition of the extracts investigated, as a result of different raw materials and extraction methods, makes comparison of the studies very difficult. Clinical evidence indicates that some hawthorn extracts may increase the exercise tolerance of patients with congestive heart failure. More clinical studies are needed to establish the effects of hawthorn, especially in healthy humans.