Effect of feed gas composition of gas discharge plasmas on Bacillus pumilus spore mortality

AIMS: To investigate the effect of gas composition on the sensitivity of Bacillus pumilus spores to gas plasmas. METHODS AND RESULTS: Inert gas plasmas, oxygen-based plasmas and various moisturized air plasmas were used to inactivate B. pumilus spores in low gas pressure of 50 Pa. Although the treatment temperature did not exceed 55 degrees C when exciting these plasmas, spore survival varied widely depending on the composition of the gas feed. Higher spore mortality was acquired by inert gases of low molecular weight except for helium. The highest spore mortality (4.54log reduction) was obtained when air with a 0.05 molar fraction of water vapour was used as the plasma carrier gas. CONCLUSIONS: Water molecules in the plasma carrier gas play a significant role in inactivation of B. pumilus spores. SIGNIFICANCE AND IMPACT OF THE STUDY: This strong inactivation may occur through hydroxyl free radicals generated from the moisturized air plasma.     

Inhibition of aflatoxin production of Aspergillus parasiticus NRRL 2999 by Bacillus pumilus

Six isolates of Bacillus pumilus were tested for their ability to inhibit aflatoxin production of Aspergillus parasiticus NRRL 2999 in yeast extract sucrose (YES) broth. Aflatoxin production was inhibited in both simultaneous and deferred antagonism assays, suggesting that the inhibitory activity was due to extracellular metabolite(s) produced in cell-free supernatant fluids of cultured broth. The inhibition was not due to organic acids or hydrogen peroxide produced by B. pumilus since the inhibitory activity was not lost after pH adjustment or treatment of supernatant fluids with catalase. A range of media tested for the production of inhibitory metabolite(s) in supernatant fluids showed that all media supported bacterial growth and production of the metabolite(s). The metabolite(s) were produced over a wide range of temperature (25 to 37°C) and pH (4 to 9) of growth of B. pumilus. They were stable over a wide range of pH (4 to 10) and were not inactivated after autoclaving at 121°C for 30 minutes. This revised version was published online in August 2006 with corrections to the Cover Date.     

利用淀粉的碱性蛋白酶工程菌的培养条件

自70年代开始,国内曾筛选出短小芽孢杆菌(Bacillus pumilus) 289、209两株产碱性蛋白酶的菌株。由于这两个菌株以葡萄糖为速效碳源,菌株产碱性蛋白酶的能力受培养基中总糖的制约,且两株菌易受短小芽孢杆菌烈性噬菌体PP_1—PP_10。的感染,因而不利于作为碱性蛋白酶制剂生产用菌。作者已从制革厂毛泥池中分离得到一株碱性蛋白酶产生菌——短小芽孢杆菌cl72,该菌株对PP_1—pp_10。噬菌体不敏感,对地衣芽孢杆菌pL_1噬菌体亦无交叉感染,是野生型的噬菌体抗性菌株。C172菌无淀粉酶基因,仍     

芽孢杆菌基因工程新载体的构建

利用从Bacillus pumilus 289中分离出的隐秘质粒pNK289(7.2kb)的复制起始调控区及启动区DNA片段和质粒pPL 601上的氯霉素乙酰基转移酶结构基因(cat-86),构建了能在B.subtilis和B. pumilus中稳定传代的质粒pNQ216(4.1kb)和pNQ402(2.8kb)。在非诱导条件下,其在含Cm的LB平皿上的外显率都比pPL600高约30％,可以用作芽孢杆菌基因克隆的质粒载体。     

甜菜增产菌P10菌株的鉴定

在新疆甜菜块根皮层内分离并筛选到对甜菜具有增产增糖作用的优化菌株Ｐ＿（１０）。通过形态培养征和生理生化特性研究,将该菌株鉴定为短小芽孢杆菌（Ｂａｃｉｌｕｓｐｕｍｉｌｕｓ）。     

产耐碱性β-1，4-聚糖酶芽孢杆菌A-30液体发酵研究

研究了搅拌转速、ＰＨ控制以及插瓶发酵过程中不同时间硫酸铵的补加对β－１,４聚糖酶形成的影响,优化得到Ａ－３０的β０１,４－聚糖酶分批发酵操作条件和初步优化了（ＮＨ４）２ＳＯ４流加发酵条件。研究结果显示麸皮表面有大量Ａ－３０菌体细胞的吸附,搅拌转速对菌体吸附和β－１,４－聚糖酶的形成有明显影响;发酵过程中ＰＨ下降有利于β－１,４－聚糖酶形成。采用了实期以５ｍｌ／ｈ的速率恒速流加,后期测定（ＮＨ４）２     

短小芽孢杆菌HZbp脂肪酶基因的克隆表达

以短小芽孢杆菌HZbp总DNA为模板以PCR的方式获得512 bp的脂肪酶基因,并在该基因的两端引入了EcoR1和Sal1的酶切位点,将该基因与大肠杆菌表达质粒pSE380连接,获得重组质粒pSE380-BPL。重组质粒转入大肠杆菌表达细胞株BL21,获得工程菌株BL21-BPL。序列分析显示所克隆的基因具有脂肪酶的保守G-X-S-X-G序列,SDS-PAGE电泳显示该脂脂肪酶的分子质量约为20 kDa。在LB培养基中,IPTG诱导浓度为1.0 mmol/L,33℃诱导培养10 h后,发酵液酶活达到8 U/mL。     

发酵过程中溶氧浓度对D-核糖发酵的影响

通过固定不同溶氧浓度(DOT)对短小芽孢杆菌(Bacillus pumlus)进行分批发酵的过程参数变化的比较,发现发酵前期与后期对氧的需求不尽相同,探讨了氧代谢途径及溶氧浓度对核糖发酵的影响机理,并提出分阶段供氧模式。结果表明,发酵时间44h后,整个发酵过程保持了较高的核糖产率和葡萄糖消耗率,最终核糖产量和细胞生成量分别提高了5.0％和18.8％。     

短小芽孢杆菌碱性蛋白酶基因启动子的克隆、鉴定及其应用

利用TAIL-PCR(Thermal asymmetric interlaced PCR)从短小芽孢杆菌基因组中扩增到碱性蛋白酶基因编码区上游的启动子片段。对该片段的序列测定和分析表明, 此片段长797 bp, 但与基因表达有关的序列长约390 bp。对启动子片段进行不同长度的缺失突变, 以获得最小的基因启动子片段, 结果表明, 该基因起始密码子上游约160 bp的DNA片段就可以启动基因的表达。将含有该片段的碱性蛋白酶基因WApQ3插入大肠杆菌-芽孢杆菌穿梭质粒载体pSUGV4中, 构建了碱性蛋白酶基因表达质粒pSUBpWApQ3。将该质粒分别转入枯草芽孢杆菌和短小芽孢杆菌中表达, 可在胞外检测到碱性蛋白酶活性, 最高酶活分别为466.5 U/mL和3060 U/mL。