延长初发酵培养时间对大肠菌群结果影响分析

阐述了将《大肠菌群多管发酵法》(GB/T 4789.28-2003)初发酵时间24h延长至48h的原因,通过对139份不同种类样品进行大肠菌群总数检测,发现有12份样品增加了大肠菌群数,表明延长初发酵培养时间,可以增加迟缓发酵大肠菌群成员检出。指出迟缓发酵大肠菌群在44.5℃培养时,均无产酸产气现象,表明引起迟缓发酵的大肠菌群不属于粪大肠菌群成员。

延长初发酵培养时间对大肠菌群检测结果的影响

目的:为了解延长初发酵培养时间对各类样品大肠菌群检测结果的影响。方法:依据国标法检测大肠菌群数,将初发酵培养18～24 h未产酸产气的阴性管样品继续培养至36～48 h,对7类358份样品进行大肠菌群数的检测。结果:延长初发酵培养时间至36～48 h,另有68份迟缓发酵样品检出大肠菌群,大肠菌群检出率平均提高了19.0%,各类样品大肠菌群检出率分别提高了:酱卤肉9.8%、冷菜24.4%、果汁饮料40.7%、含奶冰冻饮品21.2%、食用冰块17.1%、桶装纯净水13.2%和表面涂抹样品6.4%。比较各类样品在18～24 h和36～48 h大肠菌群数的不合格率,果汁饮料有比较显著的差异(χ2=7.0,P<0.01)。结论:延长初发酵培养时间可不同程度提高样品的大肠菌群检出率,为某些样品大肠菌群测定的国标修订提供了实验依据。

延长初发酵培养时间对大肠菌群检测结果的影响

目的为了解延长初发酵培养时间对各类样品大肠菌群检测结果的影响。方法依据国标法检测大肠菌群,将初发酵培养18～24h未产酸产气的阴性管样品继续培养至36～48h,对7类358份样品进行大肠菌群的测定。结果延长初发酵培养时间至36～48h,另有68份迟缓发酵样品检出大肠菌群,大肠菌群检出率平均提高了19.0%,各类样品大肠菌群检出率分别提高了:酱卤肉9.8%、冷菜24.4%、果汁饮料40.7%、含奶冰冻饮品21.3%、食用冰块17.1%、桶装纯净水13.2%和表面涂抹样品6.5%。比较各类样品在18～24h和36～48h大肠菌群数的超标率,果汁饮料有比较显著差异(χ2=7.0,P<0.01)。结论延长初发酵培养时间可不同程度提高样品的大肠菌群检出率,为某些样品大肠菌群测定的国标修订提供了实验依据。

响应曲面法优化大肠菌群初发酵培养基

在标准LST培养基基础上,通过单因素实验、Box-Behnken响应曲面法优化大肠菌群初发酵培养基,探讨了乳糖、胰蛋白胨和酵母粉各因素对大肠菌群菌落总数的影响。确定适宜的培养基组成为乳糖0.5g/100mL,胰蛋白胨1.64g/100mL,酵母粉0.29g/100mL。在此条件下,大肠菌群菌落总数为1.025×107cfu/mL,经验证实际值为1.033×107cfu/mL,与理论值无明显差异。

大肠菌群测定初发酵培养基的改进

用我国国家标准乳糖胆盐培养基(GB4789.3-94,简称GB)、日本卫生协会煌绿乳糖胆盐肉汤培养基(简称BGLB)和美国食品与药品管理局(FoodandDrugAdministration,简称FDA)月桂基硫酸盐胰蛋白胨肉汤培养基(简称LST)对大肠杆菌菌液以及蔬菜中的大肠菌群进行检测对比试验。结果表明:LST培养基对大肠菌群的检出率比BGLB培养基和GB培养基分别高35.93%、67.71%。以LST培养基为基础并优选出A3培养基(LST+0.2%吐温),扩大实验表明:A3培养基对大肠菌群的检出率比GB培养基和LST培养基分别高出577.12%和143.72%。

Study on the Monascus Pigment of Monascus Strains JF-02 Fermentation

[ Objective] The aim was to study the fermentation technology of monascus pigment of monascus strains JF-02. [ Method] Single factor experiment was carried out to study the influence of temperature, initial pH, culture time, different agricultural byproduct, and nitrogen source on monascus pigment in fermentation solution. Meanwhile, orthogonal experiment was conducted to get the optimal culture medium and cultivation condition. [ Resultl The optimal gene in the pigment of monascus pigment was 200 g/L of rice, 30 g/L of sweet potato powder, 10 g/L of glucose, 15 g/L of monosodium glutamate, 0.1% of zinc sulfate, and 0.1% of magnesium sulfate. The optimal culture condition was 30 ℃ and initial pH was 6.0. Fermentation time was 72 h, but when 24-L fermentation pot was used, culture time can last to 84 h. [ Condusion] The study provided theoretical basis for the development and application of monascus strains.