通过获得链霉素抗性基因突变株筛选小诺霉素高产菌株

通过链霉素对小诺霉素产生菌 (Micromonospora purpura) 49 1 2 #菌株孢子致死浓度的测定 ,采用诱变剂EMS 3种不同诱变剂量对菌株的孢子进行诱变处理 ,诱变处理的孢子涂布在含链霉素致死浓度的改良高氏平板上 ,获得大量的链霉素抗性基因突变株 ,然后从链霉素抗性基因突变株进一步筛选小诺霉素高产菌株 ,获得小诺霉素菌株 49 1 2 3菌株。在摇瓶条件下 ,其产小诺霉素生物活性单位比出发菌株 49 1 2 #的摇瓶发酵单位提高了 40 %以上。小诺霉素的组分比由出发菌株的C2b∶C1a的 5∶5提高到 8∶2。C2b有效组分提高了 30 %;链霉素抗性基因突变与小诺霉素发酵单位突变之间 ,小诺霉素正突变率达到 40 %,负突变率达 2 6%。

Screening and Taxonomic Status of a Highly Efficient Antifungal Strain against Cytospora chrysosperma

In order to look for Trichderma strains which have inhibiting effects on Cytospora chrysosperma, total 29 domestic and foreign Trichderma strains were screened by confrontation culture and growth rate method. The physiological ecology characteristics and taxonomic statuses of the screened highly efficient antifungal strains were studied. The results showed that the n-butanol extract from T-33 fer- mentation liquid showed the highest inhibition rate （94.2%） against mycelial growth, and its inhibition rate against spore germination was up to 100%. For the growth of T-33 strain, the optimum carbon source was glucose with optimum content of 3% （g/L）; the optimum nitrogen source was soy four with optimum content of 0.02% （g/L）; the optimum initial pH of culture medium was 6; the optimum culture temper- ature was 25 ℃. The 18S rDNA sequencing results showed that the full length of ITS sequence was 583 bp, and the T-33 strain was verified as Trichoderma viride.

Toxicity Screening of Several Fungicides on Tomato Basal Stem Rot

The toxicities of several fungicides to Pythium ultimum were determined by the method of mycelia growth. The results showed that hymexazol, Ovraclostrobin＋ Metiram, copper calcium sulphate, Thiophamate-merhyl and Famoxadone＋Cymoxanil all showed good inhibitory effects, of which Hymexazol was the best one with the ECho of 2.631 2 mg/L, followed by Ovractostrobin＋Metiram, whose ECso was 5.303 3 mg/L, and the effects of other fungicides were relatively poor. In the field fungicide screening test, the combination of 70% hymexazol wettable powder and 70% Thiophamate-merhyl had the control efficiency of 95.57%, which was better than the other test combinations, and it was applicable in the field control of tomato basal stem rot.

食物霉变优势菌筛选及霉变防治技术研究进展

食物霉变是一种常见的自然现象,引起该现象的主要原因是霉菌的生长繁殖。霉菌污染给人类生产和生活带来严重危害,因此,霉变的防治显得尤为重要。综述了由微生物导致的各种食品腐败变质现象,对霉菌菌种筛选、纯化分离、鉴定、生物学特性的研究进展进行梳理,并归纳了目前防霉技术的现状。

Statistical culture-based strategies to enhance chlamydospore production by Trichoderma harzianum SH2303 in liquid fermentation

Trichoderma-based formulations are applied as commercial biocontrol agents for soil-borne plant path- ogens. Chlamydospores are active propagules in Trichoderma spp., but their production is currently limited due to a lack of optimal liquid fermentation technology. In this study, we explored response surface methodologies for opti- mizing fermentation technology in Trichoderma SH2303. Our initial studies, using the Plackett-Burman design, iden- tified cornmeal, glycerol, and initial pH levels as the most significant factors （P〈0.05） for enhancing the production of chlamydospores. Subsequently, we applied the Box-Behnken design to study the interactions between, and optimal levels of, a number of factors in chlamydospore production. These statistically predicted results indicated that the highest number of chlamydospores （3.6×108 spores/ml） would be obtained under the following condition： corn flour 62.86 g/L, glycerol 7.54 ml/L, pH 4.17, and 6-d incubation in liquid fermentation. We validated these predicted values via three repeated experiments using the optimal culture and achieved maximum chlamydospores of 4.5×108 spores/ml, which approximately a 8-fold increase in the number of chlamydospores produced by T. harzianurn SH2303 compared with that before optimization. These optimized values could help make chlamydospore production cost-efficient in the future development of novel biocontrol agents.

Development of a colorimetric assay for rapid quantitative measurement of clavulanic acid in microbial samples

We developed a colorimetric assay to quantify clavulanic acid （CA） in culture broth of Streptomyces clavuligerus, to facilitate screening of a large number of S. clavuligerus mutants. The assay is based on a β-1actamase-catalyzed reaction, in which the yellow substrate nitrocefin （λmax=390 nm） is converted to a red product （λmax=486 nm）. Since CA can irreversibly inhibit β-1actamase activity, the level of CA in a sample can be measured as a function of the A390]A486 ratio in the assay mixture. The sensitivity and detection window of the assay were determined to be 50 μg L -1 and 50 μg L to 10 mg L-1, respectively. The reliability of the assay was confirmed by comparing assay results with those obtained by HPLC. The assay was used to screen a pool of 65 S. clavuligerus mutants and was reliable for identifying CA over-producing mutants. Therefore, the assay saves time and labor in large-scale mutant screening and evaluation tasks. The detection window and the reliability of this assay are markedly better than those of previously reported CA assays. This assay method is suitable for high throughput screening of microbial samples and allows direct visual observation of CA levels on agar plates.