Isolation and identification of effective cellulolytic bacteria in composting process from different sources

Cellulolytic bacteria have a bio-activating role in the composting process. A study was carried out to isolate and identify cellulolytic bacteria from various sources. The isolates were cultured in the carboxymethyl cellulose (CMC) agar medium and incubated at 30°C for 3–7 days. Based on morphological characteristics of the isolates, maximum diameter of a clear zone around the colony and maximum cellulolytic activity, eight isolate were selected for further studies regarding composting experiments.

Molecular tests based on PCR amplification and sequencing of 16S rRNA gene of isolates showed the closest phylogenetic similarity with the species of Stenotrophomonas rhizophila DSM14405 (99.8%), Brevibacterium halotolerans DSM8802 (99.6%), Achromobacter marplatensis B2 (99.8%), Bacillus methylotrophicus CBMB205 (100%), Pseudomonas azotoformans IAM 1603 (99.7%), Bacillus sonorensis NBRC 101234 (99.8%), Bacillus subtilis KCTC 13429 (100%) and Ochrobactrum thiophenivorans DSM 7216 (99.3%). The study of the isolates impact on the composting of palm wastes in a randomized complete block design with 11 treatments in 3 replications showed that strain IB (B. methylotrophicus) caused a significant decrease in C:N ratio (58%). The increasing of microbial respiration compared with control after 30 days incubation at 37°C showed that the B. methylotrophicus strain IB with cellulolytic characteristics can be applied to hydrolysis of cellulosic biomass in the composting processes.     

酶解牦牛血发酵液制备抗氧化肽工艺优化

为进一步提高牦牛血枯草芽胞杆菌发酵液多肽含量,对牦牛血发酵液进行酶解,以酶解液的·OH清除率、多肽含量为主要指标,筛选酶解发酵液的最适蛋白酶,通过单因素和响应面试验优化酶解工艺,并对比菌酶联合制备产物与发酵液体外抗氧化活性。结果表明,碱性蛋白酶酶解发酵液最佳条件为:酶解时间3 h、p H值9.5、酶解温度60℃和酶底比190 U·g-1,此条件下制备得到酶解液多肽含量为5.52mg·mL~(-1),较发酵液提高2.39倍。菌酶联合制备产物对·O2-及脂质过氧化的IC50分别为6.22、4.87mg·mL~(-1),发酵法制备产物对·O2-及脂质过氧化的IC50分别为8.42、11.71 mg·mL~(-1),且菌酶联合制备产物的还原力优于发酵制备产物。因此,菌酶联合制备牦牛血抗氧化肽法优于传统单一发酵法。本研究结果对提高牦牛血抗氧化肽得率,增加牦牛产品附加值具有重要的意义。     

鱼稻共生条件下陶粒载体水稻浮床提高细菌活性及多样性

以轻质陶粒为主要原料开发出一种新型生物浮床载体,并通过种植水稻构建了陶粒载体水稻浮床对池塘水环境进行修复。研究了陶粒载体水稻浮床对精养池塘的水质净化作用,并采用Biolog-ECO技术分析了陶粒载体水稻浮床对池塘浮游细菌碳源代谢模式和多样性的影响。结果显示,试验组池塘水中总氮(TN)、总磷(TP)和亚硝态氮(NO2–-N)等水质指标在8月份显著低于对照组,高锰酸盐指数(IMn)在8月份和10月份显著低于对照组。试验组池塘浮游细菌群落代谢活性(AWCD)、Shannon指数和丰富度指数在8月份显著高于对照塘,Shannon均匀度指数在10月份显著高于对照塘。浮床种植水稻产量达到5 900 kg/hm~2。结果表明陶粒载体水稻浮床在具备一定生产性能基础上,降低了精养池塘水中氮磷营养水平,改变了精养池塘浮游细菌群落碳源利用模式,并提高了池塘浮游细菌群落代谢活性和功能多样性。结果可为应用陶粒载体水稻浮床调控池塘水环境提供理论指导。     

Fixation of carbon dioxide by chemoautotrophic bacteria in grassland soil under dark conditions

Grassland is one of the most important terrestrial ecosystems for carbon (C) and nitrogen (N) cycling. However, while CO₂ fixation by phototrophic bacteria is relatively well studied, little is known about microbial CO₂ fixation without light by chemoautotrophic bacteria in grassland soils. Therefore, in this study, the isotope ¹⁴C-CO₂ was used to investigate the CO₂-fixing process in grassland soils. Soil samples were collected from both fenced and adjacent continuous grazing grassland sites in Inner Mongolia and then incubated for 120 days under dark conditions. Meanwhile, the cbbL genes (red- and green-like) were analyzed to isolate chemoautotrophic bacteria, which are responsible for CO₂ fixation. After incubation, ¹⁴C was fixed into soil organic carbon (¹⁴C-SOC) and microbial biomass carbon (¹⁴C-MBC) were found in both the fenced and grazing soils, and the fixation rate of ¹⁴C-SOC in the fenced soils (48.55‰) was significantly higher than in the grazing soils (22.11‰). The fixation rate of ¹⁴C-MBC in the fenced soils (14.05‰) was higher than in the grazing soils (7.08‰), but the difference was not significant. The red-like cbbL genes could be detected in all the soil samples, but the green-like cbbL genes could not be amplified. A greater number of identified operational taxonomic units were observed in the fenced soils compared with the grazing soils. The chemoautotrophic bacteria were mainly affiliated with Alphaproteobacteria and Actinobacteria. However, Chloroflexi was detected in only the fenced soils. The results suggested that CO₂ fixation by chemoautotrophic bacteria might be significant in carbon cycling in grassland.     

不同保存方法对重组大肠杆菌菌株活性的影响

[目的]探讨不同重组大肠杆菌菌株保存的方法,找出其保存的最适条件。[方法]以携带质粒pcDNA3的大肠杆菌DI-lSct为研究对象,分析了4oC冷藏和一70℃冷冻保存对菌株活性的影响。[结果]4℃条件下,高稀释度的菌液中活细胞教随着时间的延长而逐渐上升,到第7天时达到最高峰,随后呈现逐渐下降的趋势-70℃条件下,菌液OD600值为0．8,甘油终浓度为8％的处理组,在各保存时间段的活细胞数均显著高于其他组.[结论]4℃短期保存重组菌株时,菌液最佳存放时间为7d左右;-70℃长期保存时,宜采用对数生长期的细菌,且保持甘油工作浓度8％为宜。     

木薯酒精废水脱色菌的筛选及脱色条件研究

[目的]筛选出高效的木薯酒精废水脱色菌,并探索其最佳脱色条件。[方法]分别从华南理工大学环境学院、猎德污水处理厂取得污泥,经过分离纯化和初步筛选,得到对木薯酒精废水具有脱色作用、且脱色效果稳定的1株菌株,并通过单因素试验研究以其作为出发菌的最佳脱色条件。[结果]分离纯化和初步筛选结果表明,猎德污水处理厂的9号菌脱色效率最高,为20.3%;以9号菌作为出发菌的脱色单因素试验结果表明,9号菌的最佳接种和脱色时间分别为16 h和24 h;9号菌最佳脱色条件为：以葡萄糖为外加碳源,以NaNO2为外加氮源,好氧条件,温度30℃;在该最佳条件下,其脱色能力达29.6%。[结论]单一菌种的脱色能力有限,该研究为获得脱色能力较好的复合菌群奠定了基础。     

犊牛源乳酸菌的筛选及抑菌性能研究

从15日龄健康犊牛的肠道黏膜和食糜分离得到31株革兰氏阳性、无芽孢乳酸菌。通过耐消化道环境筛选得到4株乳酸菌M5、M7、SB1和Z4,在pH=2条件下处理2h后的存活率分别为39.24%、28.08%、44.20%、23.28%,有较强的耐牛胆盐能力,经人工胃液处理后各菌的存活率均可达到30%以上,且活菌数超过108CFU/mL。能抵御体外模拟的胃肠道逆环境的影响,且对大肠杆菌的抑制作用明显,抑菌圈直径为16～21mm。     

植物根际微生物次级代谢产物研究进展

植物根际是微生物生长的特殊微生态环境,根际微生物在种类和数量上不同于非根际微生物。近年来,通过根际微生物途径分离到一些活性物质,其中有一些新结构化合物,并在多方面具有较高生物学活性。植物根际微生物是一类值得深入研究与开发的微生物资源。     

杨桃黄瓜复合汁乳酸菌发酵饮料的研制

[目的]研究了杨桃黄瓜复合汁乳酸菌发酵饮料的制作工艺。[方法]以杨桃和黄瓜为主要生产原料,以保加利亚乳杆菌和嗜热链球菌为发酵菌种,经驯化使其适应杨桃黄瓜复合汁的生长环境,并通过正交试验确定杨桃黄瓜复合汁乳酸菌发酵饮料的最佳发酵条件和最佳口感调配方案。[结果]最终确定最佳发酵条件为：杨桃汁：黄瓜汁=4：1（W／W）,脱脂牛乳添加量为10％（V／V）,接种量6％（V,发酵温度为42℃,发酵时间16h;最佳口感调配方案为：蔗糖4．0％（W／W）,柠檬酸0．2％（IV／W）,杨桃汁5．0％（W／W）。[结论]产品具有较大的开发价值和市场前景。     

接种秸秆降解真菌对玉米苗期生长的影响

利用盆栽试验接种44株可降解秸秆的丝状真菌,研究真菌对玉米发芽和苗期生长的影响。结果表明：8株真菌(F6、F7、F9、F11、F16、F17、F18和F36)可显著降低玉米发芽率(P<0.05),其中极显著两株为F6和F36,分别降低45.0%和32.5%;真菌F36同时也显著降低单株生物量,降低率为48.0%;两株真菌F5和F45可显著提高玉米苗期单株生物量(P<0.05),分别提高35.0%和48.0%。真菌F5和F45经初步鉴定分别为Fusarium sp.和Trichoderma sp.,两种真菌显著促进玉米苗期生长。