利用谷物进行类胡萝卜素固态发酵

研究了 7种谷物培养基及相关因素对青霉PT95菌株进行类胡萝卜素固态发酵的影响作用。结果表明 ,谷物培养基的组成对PT95菌株在固态发酵条件下的菌核生物量和菌核中的类胡萝卜素含量都有明显的影响 ;接种方式和接种量能明显影响谷物培养基上的菌核生物量 ,但对菌核中的类胡萝卜素含量没有明显的影响 ;在谷物培养基里添加麸皮有利于菌核的形成。在选择最佳接种方式、接种量 ,并在培养基里添加 2 0 %麸皮 (干重 )的固态发酵条件下 ,大米培养基上得到的菌核生物量最高 ,达到 1 5 0 0 g/1 0 0 g(干料 ) ;荞麦培养基上 ,菌核中的类胡萝卜素含量最高 ,达到82 6μg/g(干菌核 ) ;而在谷子培养基上 ,类胡萝卜素产率最高 ,达到 1 1 45 7μg/1 0 0 g(干料 )。     

Intraspecific variability of growth and patulin production of 79 Penicillium expansum isolates at two temperatures

Penicillium expansum is the main species responsible for patulin production in apples and pears. Generally, fruit is stored at suboptimal conditions for mould growth and this situation could influence on the intra-species variability in both capability for growth and mycotoxin production. The aim of this research was to assess the impact of suboptimal environmental conditions on the intra-specific variability of P. expansum growth and patulin production using seventy nine isolates of this mould. Petri dishes with Apple Concentrate Agar Medium (ACAM) were inoculated centrally and incubated at two temperatures, one near optimal (20 °C) and the other representative of suboptimal cold storage (1 °C). For each condition, 10 Petri dishes were inoculated, and colony growth and patulin production was measured over time. The Kruskal-Wallis test revealed significant differences among growth rate (μ) and lag phase (λ) within the seventy nine assayed isolates. Coefficients of variation revealed a wider dispersion of μ (mm/day) and λ (days) at 1 °C compared with 20 °C. There were significant differences (p < 0.05) among patulin levels (ng/mm²) for the different conditions, values being lower at the lower temperature. Coefficients of variation revealed a wider dispersion of mycotoxin production at 1 °C. In order to address the strain variability in growth initiation and prove the well-established notion of reducing patulin production in foods by preventing fungal growth, a greater number of strains should be included.     

槐糖脂对蜜橘果实采后青霉病的控制及其机理

从自然发病的蜜橘果实上分离出一株致病真菌,通过形态学特征、rDNA-内转录间隔区（rDNA-internal transcribed spacer,rDNA-ITS）分析以及致病性检测,发现该真菌为柑橘意大利青霉（Penicillium italicum）。离体实验发现,当槐糖脂质量浓度为0.1?g/L时,青霉的生长被完全抑制;在果实实验中,当槐糖脂质量浓度为35?g/L时,蜜桔果实的病斑直径最小,且发病率最低。采用质量浓度为35?g/L的槐糖脂对蜜桔果实进行接种和浸泡处理,均能有效提高蜜桔果实的抗病性,且蜜桔果皮的过氧化物酶、多酚氧化酶和苯丙氨酸解氨酶的活力得到了提高。该实验为蜜桔果实采后青霉病的防治提供了一定的理论依据。     

大曲中放线菌和青霉产酶初探

以从大曲和糟醅中分离出的放线菌和青霉为研究对象,用淀粉培养基和纤维素刚果红培养基对两种菌分别进行初筛,根据透明圈和菌落直径之比大小筛选出产淀粉和纤维素酶的菌株,进一步通过固体发酵培养并测定淀粉酶和纤维素酶活,筛选出三株分解淀粉和纤维素的菌株命名为放线菌F1,青霉Q4,青霉Q5,其中青霉Q4的两种酶活力都较高,α-淀粉酶活达到1160u/g干曲,内切纤维素酶活达到301.83u/g干曲,滤纸酶活达到48.26u/g干曲。     

扩展青霉侵染柑橘机制分析

从细胞壁降解酶的角度利用转录组技术分析扩展青霉（Penicillium expansum）侵染柑橘的机制。P. expansum H1在改良的Marcus培养基和柑橘体内均可以产生细胞壁降解酶聚半乳糖醛酸酶、果胶甲基半乳糖醛酸酶、内切β-1,4-葡聚糖酶和β-葡萄糖苷酶。同时,与P. expansum H1侵染柑橘相关的基因表达量均上调,如与细胞壁降解相关的基因、与桔霉素产生相关的基因、与宿主pH值改变相关的基因、与抗氧化应激反应相关及与效应因子相关的基因。结果表明：在P. expansum H1侵染柑橘的过程中,细胞壁降解酶、桔霉素、pH值、抗氧化酶等均起到重要的作用。     

壳聚糖对柑橘青、绿霉病病原菌的抑菌效果研究

应用PDA培养基多次分离并纯化培养得到柑橘青霉病病原菌、绿霉病病原菌,加入不同浓度壳聚糖的PDA培养基对两种病原菌进行接种培养并观察抑菌效果。结果表明:壳聚糖对两种病原菌有一定的抑制能力,其中对青霉病病原菌的抑制能力强。壳聚糖浓度为1.3%时抑制率最高,在第2d时对青、绿霉病病原菌的抑制率分别达到71.5%、46.37%。     

钼酸铵和焦亚硫酸钠对采后苹果青霉病和黑斑病的控制

研究了GRAS物质钼酸铵和焦亚硫酸钠处理对苹果青霉病和黑斑病的控制,结果表明在离体条件下,钼酸铵和焦亚硫酸钠均能抑制Penicillium expansum和Alternaria alternate菌落的生长,其中7.5 g/L钼酸铵、0.3 g/L焦亚硫酸钠抑制效果最佳,其抑菌率分别达到78.7%、72.7%、81.3%、56.3%。体内试验表明,钼酸铵和焦亚硫酸钠对损伤接种苹果的青霉病和黑斑病也有一定的控制作用,其中7.5 g/L的钼酸铵对苹果青霉病的抑制效果最佳,0.25 g/L的焦亚硫酸钠对苹果黑斑病抑制效果最佳。     

Purification and Characterization of a Halotolerant Alkaline Serine Protease from Penicillium citrinum YL-1 Isolated from Traditional Chinese Fish Sauce

A halotolerant alkaline serine protease from Penicillium citrinum YL-1 which was isolated from traditional Chinese fish sauce was purified by ammonium sulfate precipitation, dialysis, and DEAE 52-Cellulose column, thereby resulting in a 4.66-fold increase in specific activity (110.68 U/mg). The molecular weight (MW) was estimated to be 32.27 kDa using SDS-PAGE analysis. The protease exhibited optimal activity toward the substrate casein at pH 8.0 at 40°C and was stable at pH 6.0–8.0 and 4–30°C. Activity was inhibited by NaCl and retained at 28.3, 21.4 and 18.1% of the initial activity after incubation for 6 h at 20, 25 and 30% NaCl concentrations, respectively. The enzyme was stimulated by Mn²⁺ and inhibited by K⁺, Ca²⁺, Zn²⁺, Mg²⁺, Fe²⁺, and Fe³⁺. K_m and V_max of the protease for casein were 1.93 mg/ml and 56.81 μg/(min·ml), respectively. Protease activity was strongly inhibited by phenylmethyl sulfonylfluoride (PMSF), which confirmed the serine protease nature of the enzyme. The protease can hydrolyze tilapia protein in the absence or presence of NaCl (5–30%), thus suggesting that this protease is more halotolerant than the protease from other bacteria with high salinity resistance based on the current literature. These properties make the halotolerant alkaline serine protease a suitable candidate enzyme for fish protein hydrolysis during fish sauce fermentation.     

传统发酵豆酱中产脂肪酶菌株的筛选

脂肪酶属于羧基酯水解酶类,能将甘油三酯逐步地水解成甘油和脂肪酸。该研究从东北三省传统的家庭自制豆酱上获得纯培养真菌389株,通过三丁酸甘油酯平板法初筛获得具有脂肪酶活性的菌株41株,其中青霉属的真菌27株、曲霉5株、毛霉3株、犁头霉2株、酵母菌1株、镰孢菌2株、帚霉菌1株。结果表明,青霉属的真菌无论从数量还是酶活都高于其他属的真菌,其中橘灰青霉（Penicillium aurantiogriseum）数量最多。在分离到的菌株中,毛霉属的卷枝毛霉（Mucor circinelloides）酶活最高,是具有生物催化潜力的功能菌株。