利用大米固态发酵生产球孢白僵菌的工艺优化

以孢子粉含孢量、含水量及活孢率为质量指标,以单位质量基质产孢数为产量指标,对大米固态发酵生产球孢白僵菌高孢粉的发酵条件进行优化。结果表明,发酵条件为:接种量15%(v/w),初始基质含水量40%,培养温度25℃,环境湿度前4d为100%,中间3d为80%,后3d为60%,培养10d。此条件下,孢子粉含孢量达到(1.93±0.08)×10~(11)g~(-1),含水量为(10.4±1.1)%,活孢率为(97.3±2.1)%,单位质量大米孢子粉产量达到(41.6±2.0)×10~(11)kg~(-1)。     

Biosynthesis of the 2-pyridone tenellin in the insect pathogenic fungus Beauveria bassiana

Genomic DNA from the insect pathogenic fungus Beauveria bassiana was used as a template in a PCR with degenerate primers designed to amplify a fragment of a C-methyl transferase (CMeT) domain from a highly reduced fungal polyketide synthase (PKS). The resulting 270-bp PCR product was homologous to other fungal PKS CMeT domains and was used as a probe to isolate a 7.3-kb fragment of genomic DNA from a BamH1 library. Further library probing and TAIL-PCR then gave a 21.9-kb contig that encoded a 12.9-kb fused type I PKS-NRPS ORF together with ORFs encoding other oxidative and reductive enzymes. A directed knockout experiment with a BaR cassette, reported for the first time in B. bassiana, identified the PKS-NRPS as being involved in the biosynthesis of the 2-pyridone tenellin. Other fungal PKS-NRPS genes are known to be involved in the formation of tetramic acids in fungi, and it thus appears likely that related compounds are precursors of 2-pyridones in fungi. B. bassiana tenellin KO and WT strains proved to be equally pathogenic towards insect larvae; this indicated that tenellin is not involved in insect pathogenesis.     

温度对球孢白僵菌生物学特性的影响

研究了不同温度对球孢白僵菌生长的影响,结果表明在22~26℃温度范围内球孢白僵菌落个数随温度的升高而逐渐增多,在26℃时达到最大。随后随着温度的升高菌落个数逐渐降低。     

Fungal Biotransformation of 2′-Methylflavanone and 2′-Methylflavone as a Method to Obtain Glycosylated Derivatives

Methylated flavonoids are promising pharmaceutical agents due to their improved metabolic stability and increased activity compared to unmethylated forms. The biotransformation in cultures of entomopathogenic filamentous fungi is a valuable method to obtain glycosylated flavones and flavanones with increased aqueous solubility and bioavailability. In the present study, we combined chemical synthesis and biotransformation to obtain methylated and glycosylated flavonoid derivatives. In the first step, we synthesized 2′-methylflavanone and 2′-methylflavone. Afterwards, both compounds were biotransformed in the cultures of two strains of entomopathogenic filamentous fungi Beauveria bassiana KCH J1.5 and Isaria fumosorosea KCH J2. We determined the structures of biotransformation products based on NMR spectroscopy. Biotransformations of 2′-methyflavanone in the culture of B. bassiana KCH J1.5 resulted in three glycosylated flavanones: 2′-methylflavanone 6-O-β-d-(4″-O-methyl)-glucopyranoside, 3′-hydroxy-2′-methylflavanone 6-O-β-d-(4″-O-methyl)-glucopyranoside, and 2-(2′-methylphenyl)-chromane 4-O-β-d-(4″-O-methyl)-glucopyranoside, whereas in the culture of I. fumosorosea KCH J2, two other products were obtained: 2′-methylflavanone 3′-O-β-d-(4″-O-methyl)-glucopyranoside and 2-methylbenzoic acid 4-O-β-d-(4′-O-methyl)-glucopyranoside. 2′-Methylflavone was effectively biotransformed only by I. fumosorosea KCH J2 into three derivatives: 2′-methylflavone 3′-O-β-d-(4″-O-methyl)-glucopyranoside, 2′-methylflavone 4′-O-β-d-(4″-O-methyl)-glucopyranoside, and 2′-methylflavone 5′-O-β-d-(4″-O-methyl)-glucopyranoside. All obtained glycosylated flavonoids have not been described in the literature until now and need further research on their biological activity and pharmacological efficacy as potential drugs.     

Desiccation increases the efficacy of Beauveria bassiana for stored-grain pest insect control

The effect of desiccation stress on the efficacy of Beauveria bassiana for controlling stored-product insects was investigated in laboratory bioassays. The mortality of B. bassiana-treated Plodia interpunctella larvae was greater at a vapor pressure deficit (VPD) of 2.42 or 1.87 kPa than at 1.06 kPa. Moisture also had significant effects on the mortalities of adult rice weevils, Sitophilus oryzae and maize weevils, Sitophilus zeamais. Mortality of S. zeamais was higher at 2.42 and 1.87 kPa than at 1.06 kPa, while mortality of S. oryzae was higher at 1.87 kPa than at either 2.42 or 1.06 kPa. Higher control mortality at the higher two VPDs indicated that S. zeamais was less desiccation tolerant than S. oryzae. The mortalities of B. bassiana-treated adult Cryptolestes ferrugineus, larval Lasioderma serricorne and larval Oryzaephilus surinamensis were not significantly affected by VPD. These results demonstrate that dry stored-grain conditions are favorable for B. bassiana efficacy.     

利用废弃烟梗发酵生产白僵菌的响应面优化

为实现废弃烟梗资源化利用,以废弃烟梗为主要发酵底料,白僵菌产孢量为响应值,采用响应面法（Response Surface Methodology,RSM）对烟梗发酵生产白僵菌的条件进行了优化。通过Plackett-Burman（PB）试验筛选出影响废弃烟梗发酵生产白僵菌最显著的因素,设计最陡爬坡试验逼近最佳条件区域,进一步设计Box-Behnken Design（BBD）响应面优化,分析并确定最佳条件。结果表明,当培养时间为9.40 d,蛋白胨含量1.21%,酵母粉含量1.03%时,白僵菌孢子产量预测最优值为1.17×10¹⁰个/g,实际孢子产量为1.13×10¹⁰个/g,拟合度达到96.58%,白僵菌产孢量显著提高。因此,采用该方法优化得到的最佳发酵条件合理而有效,对烟草生物防治以及烟梗废料的综合利用具有实际应用价值。     

超声波破碎法提取球孢白僵菌麦角甾醇的条件优化研究

通过单因素试验和正交试验确定了筛选提取球孢白僵菌麦角甾醇的最佳条件.研究结果表明:三氯甲烷为溶剂,在浸提比为1∶250(g/mL)时,超声波处理30 min为最佳提取条件;每克干菌丝可获得7 mg左右的麦角甾醇.     

侵染马铃薯块茎蛾幼虫的球孢白僵菌对桃蚜的毒力测定

室内测定了从罹病马铃薯块茎蛾Phthorimaea operculella(Zeller)幼虫上分离到的球孢白僵菌Beauveris bassiana两菌株(Bb001，Bb004)对甘蓝桃蚜Myzus persicae(Sulzer)的毒力。运用时间-剂量-死亡率模型，对死亡率随时间和剂量的变化趋势，以及两种菌株在不同温度下对桃蚜的毒力作了分析。结果表明：两种菌株对桃蚜均具有毒杀作用，菌株Bb004在21℃下表现了较高的毒力，菌株Bb001在21℃～28℃下对桃蚜均有较强的致病力，2l℃～25℃下是两菌株共同发挥毒力最佳的温度。其中，Bb001有较宽的适宜温度范围，而Bb004适宜温度范围较小。     

Cloning and expression in Saccharomyces cerevisiae of chit2 gene from Beauveria bassiana

To study recycled trashes from shrimps and crabs in the sea through chitinase secreted by microorganisms,the chitinase gene chit2 was cloned and sequenced from Beauveria bassiana by the polymerase chain reaction(PCR),and was ligated into the yeast expression vector pYES2.The expression vector plasmid was transformed into Saccharomyces cerevisiae H158.Gene expression took place upon induction with 2% galactose.The measurement of enzyme activity shows that the expression production can be expressed in active forms and secreted to the medium.The enzyme activity approaches the peak of 0.63 U/mL when the culture time is 36 h.