高活性β-葡萄糖苷酶丹贝发酵工艺研究

本文以大豆为原料,少孢根霉为发酵菌株,在研究蒸煮时间、接种量和发酵时间3个单因素条件对丹贝中β-葡萄糖苷酶活性影响的基础上,应用Box-behnken中心组合实验方法,以β-葡萄糖苷酶活性为响应值,进一步优化丹贝的生产工艺,结果表明:蒸煮时间为20min,接种量为1.50%,发酵时间为36h的条件下β-葡萄糖苷酶活性最高,为345.63U,这可为丹贝的工业化生产提供一定的理论依据。     

米根霉直接发酵小麦淀粉废水生产L(+)-乳酸研究

【目的】研究利用米根霉(Rhizopus oryzae)As3.866直接发酵小麦淀粉废水生产L(+)-乳酸的最佳条件,为小麦淀粉废水资源化利用提供参考。【方法】以米根霉As3.866为供试菌种,以小麦淀粉废水为发酵培养基直接发酵生产L(+)-乳酸,通过摇瓶发酵培养,依次研究米根霉种龄、接种量、装液量、转速、温度、pH、中和剂种类、CaCO3添加量及添加时间对L(+)-乳酸质量浓度以及米根霉菌丝体生物量和生长状况的影响,确定最佳发酵条件,并在此基础上考察发酵后废水中COD的去除效果。【结果】得到利用米根霉直接发酵小麦淀粉废水的最佳发酵条件:米根霉种龄为18h,接种量为10%,装液量为20%,温度为26℃,pH为5.5,转速为170r/min,发酵8h后添加10g/L的CaCO3,发酵周期为52h。【结论】获得了利用米根霉直接发酵小麦淀粉废水生产L(+)-乳酸的最佳发酵条件,在该条件下,L(+)-乳酸质量浓度可达15.28g/L,废水中COD的去除率达85%。     

牛粪发酵沼液对立枯丝核菌的抑制作用

为探讨牛粪发酵沼液的抑菌机理,以立枯丝核菌为研究对象,进行了试验研究。采用平皿培养方法:培养基表面分别均匀涂布1mL5种不同处理的沼液,即不作处理沼液、沼液灭菌、离心上清液、无菌膜滤液和菌体溶液,中心接种立枯丝核菌并于生化培养箱中28℃培养96h,每12h测量立枯菌落的生长直径以计算抑制率,同时借助分子生物学手段鉴定了沼液中起抑制作用的微生物。试验结果表明菌体溶液和不作处理沼液对立枯的抑制效果较好,抑制率最高可达74%和53%,离心上清液的抑制效果次之,无菌膜滤液和沼液灭菌处理的抑制作用较弱,一般在20%以下;对沼液中的微生物菌群进行了分离、纯化与筛选,获16株菌种,并与立枯丝核菌进行对峙培养试验,其中nfd-9和nfd-16具有较强抑制作用,其他菌株几乎没有抑制作用。将nfd-9、nfd-16与立枯对峙交界面处进行了扫描电镜观察,结果显示:这2株微生物通过竞争、拮抗和重寄生等作用来抑制立枯丝核菌的生长,从而到达防止病害的目的。经分子生物学技术鉴定,确定了nfd-9和nfd-16分别为米根霉菌(Rhizopus oryzae)和哈茨木霉(Trichoderma harzianum)。研究结果为进一步了解沼液抑制真菌的机理提供一定的理论参考。     

Antioxidant and Antifungal Activity of <Emphasis Type="Italic">Verbena officinalis</Emphasis> L. Leaves

The scavenging activity against DPPH (1,1-diphenil-2-picrylhydrazyl) radical and the antifungal effect against chloroform, ethyl acetate and 50% methanolic extracts of Verbena officinalis leaves were investigated. The activity of different fractions of 50% methanolic extract and some isolated compounds were also investigated. The results suggest that 50% methanolic extract and caffeoyl derivatives could potentially be considered as excellent and readily available sources of natural antifungal and antioxidant compounds.     

两种防霉剂与丙酸的组合对青贮牧草根霉菌毒力的研究

采用抑菌圈法研究了75%百菌清、50%多菌灵与99.5%丙酸在不同浓度下组合对高寒地区青贮饲草根霉菌的毒力。结果表明:丙酸(200mg/kg) 百菌清(400mg/kg)、丙酸(200mg/kg) 多酸灵(300mg/kg)、丙酸(100mg/kg) 多菌灵(300mg/kg)组合对根霉菌的毒力没有显著差异,但其毒力均极显著地高于其他处理;以丙酸(200mg/kg) 百菌清(400mg/kg)组合对青贮牧草根霉菌的抑菌作用最佳,其毒力分别是丙酸(200mg/kg) 多菌灵(300mg/kg)组合的1.05倍和丙酸(100mg/kg) 多菌灵(300mg/kg) 组合的1.20倍。     

A coating composed of chitosan and Cymbopogon citratus (Dc. Ex Nees) essential oil to control Rhizopus soft rot and quality in tomato fruit stored at room temperature

This study evaluated the efficacy of the combined application of chitosan (CHI) and Cymbopogon citratus (Dc. Ex Nees) (lemongrass) essential oil (CCEO) to control Rhizopus stolonifer in fresh tomato (Lycopersicon esculentum Mill.) fruit at room temperature (25°C) storage. The effects of the treatment (CHI and CCEO) on some quality characteristics of the fruit, namely weight loss, firmness, soluble solids, titratable acidity, pH, ascorbic acid, color, and sensory acceptability were also assessed. The minimum inhibitory concentrations of CHI and CCEO against R. stolonifer were 8 mg/mL and 5 µL/mL, respectively. Subinhibitory concentrations of CHI and CCEO (CHI 4 mg/mL, CCEO 1.25 µL/mL), alone and in combination, inhibited fungal spore germination and damaged spore membrane integrity. The CHI-CCEO coating decreased the severity of Rhizopus soft rot in tomato fruit; however, the coating more strongly delayed the infection when the fruit were artificially contaminated after coating application. The application of the coating preserved the general quality of tomato fruit as measured using a variety of physicochemical and sensory attributes. These results indicate that coatings composed of CHI and CCEO could represent promising postharvest treatments to inhibit Rhizopus soft rot in tomato fruit.     

L-Lactic Acid Fermentation with Immobilized Rhizopus Oryzae by Vegetable Sponge

Now as a feedstock for the popular biodegradable industry, the L-lactic acid have became more and more important. L-lactic acid fermentation is studied by using Rhizopus oryzae as strain and cornstarch as carbon source. The results show that compared with PVA and cotton, vegetable sponge had the best immobilizing effect. The productivity of Llactic acid is 72 - 83 g/L when the carrier size was about 8 - 10 mm, the concentration of the cartier is 15 ml vegetable sponge per 50 ml seed medium. The immobilized cells can be steadily used in repeated fermentations for more than 4 times. Immobilized by vegetable sponge will have a well appliance in L-lactic acid industry.     

产胞内脂肪酶米根霉TZ-F2菌体形态控制的研究

[目的]研究产胞内脂肪酶米根霉TZ-F2菌体形态的控制。[方法]分别考察了碳源、氮源、初始pH以及培养转速对胞内脂肪酶、菌体干重以及菌体形态的影响。[结果]得到了最优的培养条件:地沟油40 g/L,胰蛋白胨20 g/L,初始pH 4.5,转速150 r/min。在此条件下,菌体形态基本能保持在球状,单位胞内脂肪酶活达109.45 U/g,干重达31.67 g/L。[结论]该研究为利用米根霉全细胞催化合成生物柴油提供了理论基础。     

昭通苹果早期落叶病叶中一种新病原菌的发现研究

本论文实验从昭通苹果园中采集早期落叶病叶中分离得到一种新的病原菌。经培养观察,该病原菌在28℃时,2天长满整个培养基平板,刚长出的菌丝呈现白色,逐渐变为浅褐至褐色,背面菌丝也由白色变为浅灰至浅黄色。对病原菌进行显微观察,其显微观察结构为,菌丝为无隔菌丝,具有假根和匍匐枝,孢囊梗与假根相对生长,孢囊梗不分枝。孢囊孢子数量多,呈球形、卵形或不规则形。经培养特性和显微结构观察确定,该病原菌为匍枝根霉菌,是早期落叶病叶上发现的一种新的病原菌。     

Hot-water baths,biologicals and re-curing effects on rhizopus soft rot during sweetpotato packing

Rhizopus soft rot (RSR) caused by Rhizopus stolonifer is one of the most devastating postharvest diseases of sweetpotato. It causes greatest losses when sweetpotatoes are removed from storage, washed and packed for marketing. The disease has been managed effectively by prophylactic application of synthetic fungicides on the packing line. However, there is increasing demand for alternative management strategies that do not rely on prophylactic use of synthetic fungicides. While curing immediately after harvest is a standard industry practice, re-curing after storage is not widely practised for postharvest disease management. In this study, the use of hot-water baths, biocontrol agents and re-curing after storage were investigated as potential replacements for synthetic fungicides that are widely used during sweetpotato packing. Hot-water baths at 52 °C for 10–15 min immediately after inoculation reduced RSR incidence by as much as 75%, but increased susceptibility to post-treatment Rhizopus infection. The biological control product Bio-Save® (a.i. Pseudomonas syringae strain ESC-10), used in conjunction with a 4 min water bath at 52 °C, gave similar protection (1.2% RSR, t = −1.7, P = 0.514) as the industry standard treatment with dicloran. Re-curing for as little as 4 h after washing roots significantly reduced RSR and deserves further evaluation to optimize conditions and determine its influence on other postharvest diseases.