Effects of pH and temperature on products and bacterial community in L-lactate batch fermentation of garbage under unsterile condition

Acidogenesis fermentation of artificial garbage without sterile condition was conducted in batch mode to investigate effects of cultivation pH (5.5, 6.0, 6.5) and temperature (45, 50, 55 degrees C). Bacteria exiting natively in the garbage were utilized in this study; in turn, no specific seed was inoculated. The results indicated that only one set of operational conditions (pH 5.5 and 55 degrees C) led to L-lactate fermentation. Obtained yield of lactate based on initial carbohydrate was around 0.5 and optical purity of L-lactate was around 99%. In this study, three typical cases, which were L-lactate, racemic lactate and butyrate fermentation, were observed depended on sets of cultivation pH and temperature. Microbial structures of typical cases were also identified with using 16S rDNA libraries. The analysis indicated that Bacillus coagulans produced L-lactate. Lactobacillus amylolyticus, which produces racemic lactate, and Clostridium thermopalmarium, which produces butyrate, were also detected on each typical sample. L. amylolyticus and C. thermopalmarium would be eliminated by setting cultivation temperature of 55 degrees C and above, and pH 5.5 and below, respectively. From a series of this study, operational conditions of pH 5.5 and temperature of 55 degrees C would be potentially suitable for L-lactate fermentation of garbage with view of efficiency and stability of its production.     

石油污染土壤对植物种子发芽的影响研究

通过观察不同植物接种高效石油降解菌I（芽孢杆菌属）在水模拟、无污染土壤以及不同石油污染浓度土壤条件下的生长情况,记录种子发芽数,就石油污染土壤对植物种子发芽的影响进行了研究。结果表明,培养15d后,I菌预浸泡能促进种子发芽;无污染土壤培养条件下,一直浇灌I菌,种子的发芽数相对未加菌组有所降低,说明无污染条件下一直浇灌I菌对植物种子发芽有抑制作用;不同石油污染浓度条件下,种子发芽数随污染浓度升高而降低,加菌组发芽数均高于未加菌组,表明污染条件下I菌能促进植物种子发芽。     

蜡状芽孢杆菌JL好氧脱色偶氮染料的特性研究

研究了蜡状芽孢杆菌JL在好氧条件下对偶氮染料脱色的特性。试验结果表明,菌株JL在好氧条件下使偶氮染料酸性大红3R脱色的最适条件为:外加碳源为葡萄糖和酵母膏,其中葡萄糖质量浓度为2.5 g/L,酵母膏质量浓度为1 g/L,pH介于3～7,温度在30～35℃。在最适条件下,菌株JL能够使6种不同结构的偶氮染料脱色。并且脱色产物成分分析表明偶氮染料能够被还原为芳香胺。研究表明菌株JL在偶氮染料废水处理中具有潜在的应用前景。     

芽孢杆菌生长特性的研究

研究了14株常见芽孢杆菌在不同的水分活度和pH值条件下的生长特性.结果表明:芽孢杆菌对低水分活度(＜0.86)和低pH值(＜4.4)的耐受性均有限,使用柠檬酸来调节pH值能达到更好的抑菌效果.     

苯丙氨酸脱氨酶发酵工艺及其酶学性质研究

选育出一株具有较高苯丙氨酸脱氨酶活性的菌株巨大芽孢杆菌AS1.127-NJU10。考察了该菌的发酵产酶条件,结果表明:蔗糖为最佳碳源、酵母浸膏和NH4C l组成最佳氮源,其质量浓度分别为:ρ(蔗糖)=20 g/L,ρ(酵母浸膏)=2 g/L和ρ(NH4C l)=10 g/L;发酵培养基最适pH=6.5,培养温度为37℃;诱导物ρ(L-苯丙氨酸)=1 g/L时,酶活最高达1 070 U。同时对苯丙氨酸脱氨酶的性质进行了研究,结果表明:该酶最适pH=5.8,最适温度为40℃,反应液中添加φ(吐温-80)=0.2%和c(K+)=10-5mol/L能明显提高酶活。     

一株牛蒡表面产纤维素酶细菌的分离鉴定

从牛蒡表面获得的多株产纤维素酶细菌中筛选到一株产酶活性较高的菌株NP10。使用生物技术方法获得了NP10长度为1419bp的16S rDNA序列。利用生物信息学方法在美国国立生物技术信息中心NCBI基因库比对分析了该序列,通过分析初步确定该菌为Bacillus sp.。本文为食品科学中进行细菌鉴定提供了方法参考,并为开发新型纤维素酶提供了资料。     

Biotransformation of 12-hydroxyoctadecanoic acid to 12-hydroxyoctadecanamide by Bacillus cereus 50

A new microbial isolate (Bacillus cereus 50) transformed 12-hydroxyoctadecanoic acid to 12-hydroxyoctadecanamide when grown aerobically in 1% yeast extract medium at 30°C, shaken at 250 rpm for 2 to 5 d. The compound was purified by thin-layer chromatography and characterized by infrared, gas chromatography, mass spectrometry, and nuclear magnetic resonance. The yields of 12-hydroxyoctadecanamide were 9.1 and 21.5% after 2 and 5 d, respectively.     

好氧反硝化芽孢杆菌JD-014的分离鉴定及脱氮性能

为了更好地实现以绿色环保的方式处理食品工业废水中的氮素污染物,从某河道水体中分离筛选出了1株具有好氧反硝化功能的芽孢杆菌JD-014。通过对该菌株在脱氮过程中气态氮(N₂)的产生、氮平衡估算以及酶活测定证实了菌株JD-014的好氧反硝化途径,并对影响其脱氮性能的环境因素进行了研究。结果表明:以50 mg/L NO₃^--N为唯一氮源时,菌株JD-014对NO₃^--N的去除速率为0.56 mg/(L·h)。在脱氮过程中,该菌株可将NO₃^--N部分转化为N₂并伴随有相关功能酶活的检出;当碳源为丁二酸钠和柠檬酸钠、碳氮比(C/N)为10~25、温度为37℃、转速为150~200 r/min、盐度为1%以下时,该菌株脱氮性能最佳。此外,菌株JD-014还具有较好的亚硝酸盐耐受性,在NO₂^--N质量浓度为10~200 mg/L时,脱氮率可保持在46.62%~99.92%。本研究表明,好氧反硝化芽孢杆菌JD-014在实际食品加工废水的氮素污染生物处理方面具有很大的应用潜力。     

Establishing processing conditions for canning cowpea seeds in tomato sauce

The thermal process time and sensory attributes of Ife-BPC cowpeas canned in tomato sauce were studied. Heat resistance of Bacillus stearothermophilus 1518 was determined by the plate count method at 114.5 and 120.6°C. Surviving spores were cultured and TDT curves were plotted from these data to obtain D values of 2.2 ± 0.2 min at 120.6°C and 7.5 ± 0.5 min at 114.5°C. Heat penetration studies were conducted on two can sizes and at two operating temperatures. Thermal process parameters were determined using both the general and formula methods. There was no significant difference ( P < 0.05) in the process times determined by the two methods although slightly higher values were obtained with the formula method. The medium can size required a longer process time to approach the retort temperature than the small can size. The lethal effect of sterilizing at 120.6°C resulted in a lower D-value, higher sterilizing value (F₀), and higher safety ratio (a/b) than at 114.5°C. The final F₀ at the end of processing was greater than the targeted F₀ (11.0 min) from the 5D value, suggesting that the processing time is adequate for safe food production. Taste panel assessments were conducted to identify optimal processing conditions. The sensory attributes of dry and semi-dry Ife-BPC cowpeas canned in tomato sauce were compared with those of imported baked beans. Semi-dry processed cowpeas had high consumer preference over the dry seeds, and acceptable canning qualities similar to those of the imported baked beans.