产胞外多糖多功能促生菌的筛选鉴定及促生评价

【目的】探究产胞外多糖(exopolysaccharides,EPS)菌株在促进盐碱土中植物生长,改善土壤性能等方面的影响,为研制适用于盐碱土壤修复的微生物菌剂奠定基础。【方法】从新疆喀什地区盐碱草地根际土壤中筛选产胞外多糖菌株,基于16S rRNA基因序列比对及系统发育分析对产胞外多糖菌株进行种属鉴定,采用单因素和响应面法优化最高产菌株的培养基组分,通过接种试验评估其对盐碱土栽培植物的促生效果及土壤团聚体的影响。【结果】共筛选出19株具有产胞外多糖能力的菌株,隶属于7个菌属,以假单胞菌属(Pseudomonas)占绝对优势。菌株产糖量介于236-1544 mg/L,尤以泛菌属Pantoea MQ A0产糖量最高,且兼具固氮、产吲哚乙酸(IAA)和铁载体、解磷等功能。MQ A0的最适产糖发酵培养基为甘油12.5 mL/L,蛋白胨9.0 g/L,酵母粉5.5 g/L,CaCO_(3)5.1 g/L,在此条件下菌株产糖量达2436 mg/L,较优化前增加57.8%。接种MQ A0发酵液使盐碱土栽培的玉米株高、鲜重、茎粗、须根数和总根长分别提高41.2%、203.0%、42.7%、30.4%和99.7%;粗多糖提取液对土壤团聚体的形成也有显著促进作用(P<0.05)。【结论】高产胞外多糖菌株MQ A0兼具多种促生特性,在促进盐碱土中植物生长和土壤改良方面效果显著。

产胞外多糖的近海海洋细菌的筛选

海洋微生物是海洋生物的重要组成部分,海洋微生物可产生大量不同于陆生生物的活性物质,是重要的海洋药物资源。实验所用泥样采集于黄海近海海岸,对其进行海洋细菌的分离与纯化,获得了25株纯化的海洋细菌。采用苯酚-硫酸法和乙醇沉淀法检测这些菌株的发酵液中是否含有胞外多糖,进一步筛选出胞外多糖的高产菌株。实验结果表明,胞外多糖产量高于0.22g/L的菌株共7株,占总测定菌株数的28%,胞外多糖产量高于0.20g/L的菌株共13株,占总测定菌株数的52%,有48%的菌株胞外多糖产量介于0.19g/L和0.20g/L之间。其中以MBN003中多糖含量为最高,产量达到0.2305g/L。此研究结果表明MBN003菌株具有较高的产胞外多糖能力,可以选用MBN003作为胞外多糖提取物研究的来源。

一株高产胞外多糖巨大芽孢杆菌的筛选鉴定、发酵条件优化及其对土壤团聚体的影响

【目的】筛选具有高产胞外多糖(exopolysaccharides,EPS)特性的微生物菌株,为功能性土壤改良菌剂的研制提供菌种资源。【方法】采用LB-苯胺蓝平板结合菌丝拉丝法定性筛选获得具有产EPS特性的植物根际促生细菌(plant growth promoting rhizobacteria,PGPR)功能菌株;采用低温醇沉分离、硫酸-蒽酮比色法测定PGPR功能菌株经4种培养基发酵后发酵液中EPS含量,获得具有高产EPS特性的PGPR功能菌株;以发酵液中EPS含量为衡量指标,采用正交试验对高产EPS菌株发酵条件进行优化;采用培养皿土壤培养试验,分析F1发酵液对砂壤土土壤大团聚体含量的影响。【结果】初选获得8株具有产EPS特性的PGPR功能菌株;经复选确定菌株F1具有高产EPS特性,PDA是F1产EPS的最优培养基,EPS含量为867.54μg/mL。基于形态学、生理生化特性测定,以及16SrRNA基因序列系统发育分析、全基因组平均核苷酸相似度分析,确定F1为一株巨大芽孢杆菌(Bacillus megaterium)。F1产EPS的最优培养条件:28℃、180 r/min培养24 h,在该条件下EPS产量为1 123.39μg/mL。F1应用于砂壤土进行土壤培养40 d后,粒径>0.25 mm土壤水稳性大团聚体含量比对照提高了4.44倍。【结论】F1菌株具有较强的产EPS能力,能够促进砂壤土水稳性大团聚体的形成;F1产EPS最优培养基为PDA,最优发酵条件为28℃、180 r/min培养24 h。

胞外多糖促进胁迫条件下农作物生长的研究与展望

胞外多糖是微生物分泌的一大类天然大分子活性物质,在食品、医药、化工等领域有着广泛的应用。目前,大量研究结果表明,胞外多糖是一种很好的生物源肥料,外源施加可以有效地提高农作物生长性能,激活农作物自身潜在的防御机制,以此促进不同胁迫条件下农作物的生长。本文综述了胞外多糖提高盐、干旱、重金属等胁迫条件下农作物生长及生理代谢的研究进展,进而对胞外多糖促进胁迫条件下农作物生长的机理进行了归纳和总结,并对本领域的研究热点进行了展望,旨在推进胞外多糖在农业领域的应用。

产ACC脱氨酶细菌介导的辣椒抗旱和耐盐

研究将分离后的菌类接种于辣椒,分析了干旱和盐胁迫对接种菌类辣椒的形态和生理参数的影响。结果表明干旱和盐胁迫下接种洋葱伯克霍尔德菌(B. cepacia)对植物的生长促进作用最大,而接种柠檬酸铁弗氏柠檬酸杆菌(C. feurendii)促进生长的作用最小。纯培养的B. cepacia,C. feurendii和S. marcescens菌的ACC脱氨酶活性分别为12.8±0.44,12.3±0.56和11.7±0.53μMαKB/mg/min。干旱胁迫下,B. cepacia菌产生4.893±0.06 mg/mg的胞外多糖蛋白(EPS),因此抗旱性最好;其次是C. feurendii和S. marcescens,分别产生4.23±0.03 mg/mg和3.46±0.05 mg/mg胞外多糖蛋白。非胁迫条件下接种B. cepacia菌的辣椒叶片叶绿素a含量为5.7 g/mL,即使在极端干旱胁迫期间(干旱7 d)接种菌后辣椒叶片叶绿素a仍可达2.9g/mL。高浓度NaCl胁迫下,接种B. cepacia菌的辣椒叶片叶绿素a含量为3.2 g/mL。由此可知,接种上述菌可减轻盐分对根系生长的影响,提高生物量,从而说明接种细菌可作为缓解非生物胁迫的潜在方法。

牦牛酸乳特色发酵剂的研发

通过对传统发酵牦牛酸乳中分离、鉴定的17株马克斯克鲁维酵母菌进行性能筛选,选出乳糖利用率高、产胞外多糖能力强、耐酸性的一株马克斯克鲁维酵母菌。它与实验室保存的发酵性能良好的干酪乳杆菌和嗜热链球菌组合发酵,并通过单因素试验、正交试验以确定最佳发酵条件。结果表明最佳发酵条件:菌液(浓度为1×109m L-1)体积比干酪乳杆菌∶嗜热链球菌∶马克斯克鲁维酵母菌为1∶1∶4,接种量为4%,发酵温度为35℃,加糖量为4 g/100 m L,此时感观评分达到89.20分,滴定酸度达到94.420T,综合评定值为0.775。

Production of High Quality Functional Labneh Cheese Using Exopolysaccharides Producing Encapsulated Lactobacillus Bulgaricus

Production of polysaccharides by lactic acid bacteria is vital and its technology is very important, too in dairy study. The selection ofexpolysaccharides producing encapsulated Lactobacillus bulgaricus in alginate gel and the factors affecting the production of polysaccharides such as time, temperature, pH and the growth with Streptococcus thermophilus were studied, pH 5.5 and temperature 35℃/18hr were found to be optimal for exopolysaccharides production by encapsulated L. bulgaricus and free culture yielding 600 mg/L and 380 mg/L respectively. Co-culturing L. bulgaricus with S. thermophilus increased exopolysaccharides production at 35 ℃/18hr to 660 mg/L by encapsulated cells and 400 mg/L by free culture. Results of this study were applied in the manufacture of Labneh cheese vitally containing probiotic species ofL. acidophilus, L. gasseri, L. johnsonii and protection of these bacteria by polysaeeharide produced encapsulated L. bulgaricus. The use of exopolysaccharides producing encapsulated L. bulgaricus and probiotic bacteria can provide acceptable quality to functional Labneh. This product can be used as therapeutic and diabetic milk product with highly acceptable qualities. It is noted that all of the results are the means of triplicate experiments.

Abiotic factors in colony formation:effects of nutrition and light on extracellular polysaccharide production and cell aggregates of Microcystis aeruginosa

Colony morphology is important for Microcystis to sustain a competitive advantage in eutrophic lakes. The mechanism of colony formation in Microcystis is currently unclear. Extracellular polysaccharide （EPS） has been reported to play an important role in cell aggregate formation of some phytoplankton. Microcystis aeruginosa was cultivated under varied abiotic conditions, including different nutrient, light, and temperature conditions, to investigate their effects on EPS production and morphological change. The results show that nutrient concentration and light intensity have great effects on EPS production in M. aeruginosa. There was a considerable increase in EPS production after M. aeruginosa was cultivated in adjusted culture conditions similar to those present in the field （28.9 mg C/L, 1.98 mg N/L, 0.65 mg P/L, light intensity： 100 μtmol/（m2.s））. These results indicate that abiotic factors might be one of the triggers for colony formation in Microcystis.

Effects of nutrient profiles and light regime on the production of exopolysaccharide by Porphyridium cruentum

In order to increase the yield of polysaccharides from Porphyridium cruentum and the cell biomass, we investigated several important cultural conditions such as nutrient-salts, light irradiance as well as growth conditions in the flat plate photobioreacturs （FPPBR） with different light-path. We have found that the optimal （OCM II ） was a superior medium for extracellular polysaccharide production than the f/2 and Koch medium, and the polysaccharide production with OCM II was increased by 1.79 times and 1.62 times compared with that of f/2 and Koch medium; the yields of polysaccharides were also improved by optimizing the light intensity and irradiation length Furthermore, we significantly enhanced the yields of both the biomass and extracellular polysaccharidc using a small light-path photobioreactor, and about 2.1 times increase of polysaccharide production was observed in FPPBR-30 than in FPPBR-100. Overall, the process for polysaccharides production was improved and this would facilitate further studies on such polysaccharidcs such as their antiviral and antitumor activities.