乳酸菌复合发酵大蒜风味、活性成分和微生物种群变化分析

本文以大蒜为研究对象,添加植物乳杆菌、嗜酸乳杆菌和鼠李糖乳杆菌等三种乳酸菌发酵大蒜,分析乳酸菌复合发酵大蒜在风味、活性成分和微生物种群变化等方面的特征,为大规模的大蒜发酵生产提供参考。结果显示,发酵30 d后蒜味逐渐消失,并产生香味,口感显著改善;开始发酵后,发酵液p H下降明显,10 d以后发酵液的p H基本保持在4左右;发酵开始后,SOD酶活性有所增加,并保持在250 U的较高水平;细菌群落以添加的三种乳酸菌为主,发酵开始时还伴有肠杆菌、不动杆菌、寡养单胞菌、芽孢杆菌,但发酵后期没检测到肠杆菌、不动杆菌、寡养单胞菌,只检测到三种乳酸菌和芽孢杆菌,而且乳酸菌除了刚发酵时有所降低,其他时间一直保持在较高水平。本文为乳酸复合发酵大蒜的产品开发提供了研究基础。      

兔肉发酵香肠菌种配比及发酵条件的研究

用植物乳杆菌(Lp),嗜酸乳杆菌(La)和戊糖片球菌(Pp)3个菌种进行耐盐和耐亚硝酸盐试验,观察其在不同温度条件下的生长情况,然后通过正交试验确定3者配比。试验结果表明,3个菌种均可以作为兔肉发酵香肠的发酵剂,优化的配比是1.0%,0.6%,0.3%,发酵温度为30℃,RH 90%,发酵22～24 h,接种量为10~7cfu/g。     

近红外光谱快速测定 Mortierella alpina菌丝体油脂含量

为实现玉米皮渣发酵生产微生物油脂过程中菌丝体油脂含量的实时监测,建立了菌丝体油脂含量测定的近红外定标模型。结果表明,采用偏最小二乘法(PLS)、归一化预处理方法,模型的定标集相关系数(R)及验证集相关系数分别为0.997 4和0.995 8,定标集标准偏差(SEE)为1.266 6,验证集标准偏差(SEP)为1.417 1,定标集标准偏差(SEE)与验证集标准偏差(SEP)的比值为0.893 7,这表明该方法可快速准确地测定菌丝体油脂含量。     

Rumen digestion kinetics,microbial yield,and omasal flows of nonmicrobial,bacterial, and protozoal amino acids in lactating dairy cattle fed fermentation by-products or urea as a soluble nitrogen source

The objective of this study was to evaluate the effect of a fermentation by-product on rumen function, microbial yield, and composition and flows of nutrients from the rumen in high-producing lactating dairy cattle. Eight ruminally cannulated multiparous Holstein cows averaging (mean ± standard deviation) 60 ± 10 d in milk and 637 ± 38 kg of body weight were randomly assigned to 1 of 2 treatment sequences in a switchback design. Treatment diets contained (dry matter basis) 44% corn silage, 13% alfalfa silage, 12% ground corn, and 31% protein premix, containing either a control mix of urea and wheat middlings (CON) or a commercial fermentation by-product meal (Fermenten, Arm and Hammer Animal Nutrition, Princeton, NJ) at 3% diet inclusion rate (EXP). The trial consisted of three 28-d experimental periods, where each period consisted of 21 d of diet adaptation and 7 d of data and sample collection. A triple-marker technique and double-labeled ¹⁵N¹⁵N-urea were used to were used to measure protozoal, bacterial, and nonmicrobial omasal flow of AA. Rumen pool sizes and omasal flows were used to determine digestion parameters, including fractional rates of carbohydrate digestion, microbial growth, and yield of microbial biomass per gram of degraded substrate. Fermentation by-product inclusion in EXP diets increased microbial N and amino acid N content in microbes relative to microbes from CON cows fed the urea control. Microbial AA profile did not differ between diets. Daily omasal flows of AA were increased in EXP cows as a result of decreased degradation of feed protein. The inclusion of the fermentation by-product increased nonmicrobial AA flow in cows fed EXP versus CON. Average protozoal contribution to microbial N flow was 16.8%, yet protozoa accounted for 21% of the microbial AA flow, with a range of 8 to 46% for individual AA. Cows in this study maintained an average rumen pool size of 320 g of microbial N, and bacterial and protozoal pools were estimated at 4 different theoretical levels of selective protozoa retention. Fractional growth rate of all microbes was estimated to be 0.069 h^?1, with a yield of 0.44 g of microbial biomass per gram of carbohydrate degraded. Results indicated that fermentation by-product can increase omasal flow of AA while maintaining adequate rumen N available for microbial growth and protein synthesis. Simulations from a developmental version of the Cornell Net Carbohydrate and Protein System indicated strong agreement between predicted and observed values, with some areas key for improvement in AA flow and bacterial versus protozoal N partitioning.     

Acrylic Homo- and Co-polymers Based on 2, 4-dichlorophenyl Methacrylate and 8-quinolinyl Methacrylate

The monomer 2, 4-dichlorophenyl methacrylate (2,4-DMA) was synthesized from 2, 4-dichlorophenol and characterized by conventional methods. The homopolymers of 2,4-dichlorophenyl methacrylate and its copolymers with 8-quinolinyl methacrylate (8-QMA) in different feed ratio were prepared by free radical polymerization using dimethyl formamide (DMF) as a solvent and 2,2-azobis iso butyronitrile (AIBN) as an initiator. The resulting polymers were characterized by using IR spectroscopy. Reactivity ratios of monomer were evaluated using UV-spectroscopy. Average molecular weights and polydispersity were determined by gel permeation chromatography (GPC). Solution viscosity was also obtained. The thermal analysis was carried out using TGA and DSC. The homo- and co-polymers were also tested for their antimicrobial properties against selected microorganism. The metal ion uptake capacity of synthesized copolymers was estimated by batch equilibration method using different metal ion solution under different experimental conditions. It is observed that due to the presence of pendant ester bound quinoline group, the copolymers are capable of adsorbing cations from their aqueous solution.     

木质素的微生物降解

综述了木质素微生物降解酶系及酶活性调控措施,介绍了木质素降解机制及木质素微生物降解的应用。     

Biocatalytic electrode improvement strategies in microbial fuel cell systems

Microbial fuel cells (MFCs) produce electricity as a result of the microbial metabolism of organic substrates, hence they represent a sustainable approach for energy production and waste treatment. If the technology is to be implemented in industry, low cost and sustainable bioelectrodes must be developed to increase power output, increase waste treatment capacity, and improve service intervals. Although the current application of abiotic electrode catalysts, such as platinum and electrode binders such as Nafion leads to greater MFC performance, their use is cost prohibitive. Novel bioelectrodes which use cost effective and sustainable materials are being developed. These electrodes are developed with the intention to reduce start-up time, reduce costs, extend life-span and improve core MFC performance metrics (i.e. power density, current density, chemical oxygen demand (COD) reduction and Coulombic efficiency (CE)). Comparison of different MFC systems is not an easy task. This is due to variations in MFC design, construction, operation, and different inocula (in the case of mixed-culture MFCs). This high intra-system variability should be considered when assessing MFC data, operation and performance. This review article examines the major issues surrounding bioanode and biocathode improvement in different MFC systems, with the ultimate goal of streamlining and standardising improvement processes. © 2018 Society of Chemical Industry     

Analysis of Damage on the Streptococcus mutans Immersed in Ozonated Water: Preliminary Study for Application as Mouth Rinse

Ozonated water has been demonstrated to induce significant results in terms of the elimination of microorganisms. The present study assessed the damage to Streptococcus mutans after exposure to ozonated water; the ozone generator was adjusted to provide an outlet concentration of 60 mg/L, the samples were submitted to different ozonation times 1, 2, 4, 6, and 10 mi. Scanning electron microscopy and atomic force images were obtained to identify damage to the bacteria, followed by reactive oxygen species (ROS) evaluation and microbial viability. The results showed a significant reduction in viability and the images evidenced the generation of gaps on the microbial wall and surface layer alterations. Ozone can induce significant damage to S. mutans, thus suggesting that the use of ozonated water to prevent carious lesion formation is extremely promising.