沙田柚果酒酿造工艺研究

[目的]研究沙田柚果酒的酿造工艺。[方法]以沙田柚为原料,选用ZHK-I葡萄酒酵母作为发酵菌种进行发酵酿造沙田柚果酒,对果胶酶酶解、果汁脱苦、发酵工艺及果酒澄清等工艺进行研究,确定最佳工艺参数。[结果]果胶酶水解的最佳条件为：温度45℃、酶添加量0.02%、酶解时间100min、pH值3.5;果汁脱苦最佳条件为：β-环糊精的添加量0.8%、β-环糊精作用时间60min;酒精发酵的最优条件为：发酵温度30℃、接种量6%、SO2添加量50mg/L、pH值4.2;壳聚糖添加量为0.06%时,澄清效果较佳,透光率可达94.5%。[结论]酿制出来的沙田柚果酒澄清透亮,酒味浓郁,同时具有沙田柚的特殊清香味。     

发芽粟谷中谷氨酸脱羧酶的主要酶学性质初探

[目的]探讨发芽粟谷[Setaria italica（L.）Beauv.]中谷氨酸脱羧酶（GAD）的主要酶学性质。[方法]以发芽粟谷为试材,研究发芽粟谷GAD的活性及其主要酶学性质。[结果]发芽粟谷GAD最适温度为40℃,其耐热性较差,32℃保温1 h后其酶活保持率为86.3%;发芽粟谷GAD最适pH值为5.5,在pH值5.0～5.5范围内酶活保持率在80.0%以上;发芽粟GAD对Glu的Km为22.36mmol/L,Vmax为2.28μmol/min;Ca2＋、Mg2＋、Li＋、PLP和VB6对发芽粟谷GAD活力具有促进作用,而Zn2＋、La3＋、Cu2＋起抑制作用,Mn2＋、Na＋、Fe2＋和EGTA则无显著影响。[结论]该研究可为利用发芽粟谷内源GAD富集GABA提供理论依据。     

α- 淀粉酶产生菌的分离筛选及酶学性质研究

[目的]获得在某些方面性能优良（如耐高温、耐强酸、耐强碱等）的α-淀粉酶产生菌。[方法]对α-淀粉酶产生菌进行分离筛选,并对其酶学性质进行了研究。[结果]从稀释样品涂布的淀粉筛选平板上筛选出10株有明显淀粉水解圈的单个菌株,又从中得到3株α-淀粉酶酶活力较高的菌株：X6、X8和X10。这3株菌的最适pH值均在中性范围内,最适温度均为60℃。Ca2＋能提高酶的热稳定性,X6和X8在Ca2＋浓度为0.02～0.04 mol/L时,酶的热稳定性最高;X10在Ca2＋浓度为0.03～0.04 mol/L时,酶的热稳定性最高;当Ca2＋浓度继续增大时,酶的热稳定性反而降低。[结论]为满足不同行业对不同特征α-淀粉酶的需求提供了理论依据。     

一株嗜热纤维素酶生产菌的分离、鉴定及酶学研究

[目的]对一株嗜热纤维素酶生产菌进行分离、鉴定及酶学研究。[方法]从草堆下土壤中分离筛选得到一株纤维素酶生产菌,根据形态观察和16S rRNA序列分析对其进行鉴定,并对该菌的产酶条件和酶的稳定性进行研究。[结果]将分离得到的菌株命名为BSC6-1,并确定该菌可能属于芽孢杆菌(Bacillus sp.)的一个新亚种。该菌的最佳发酵培养基为1%CMC-Na,0.2%K2HPO4,0.05%MgSO4·7H2O,1%蛋白胨,0.002%CaCl2,0.000 4%FeSO4,pH 7.0。在接种量为7%的条件下,55℃培养5 d后,该菌产酶量达最高,羧甲基纤维素酶活(CMCA)与滤纸酶活(FPA)分别达10.25和8.90 U/ml。该纤维素酶的最佳酶促反应条件为55℃、pH 7.0。在温度低于70℃的条件下,该酶的相对酶活力保持在73%以上,证明该酶具有热稳定性;在pH 6.5~8.0范围内,该酶的相对酶活力保持在90%以上。[结论]该研究为BSC6-1菌株在纤维素资源方面的开发和利用提供了理论和技术基础。     

双峰驼粪便中纤维素分解菌的筛选及酶学特性分析

旨在从双峰驼粪便中筛选能够分解纤维素的菌株,并对分离菌株进行鉴定和酶学特性分析。采用羧甲基纤维素平板法初筛和摇瓶发酵法复筛,从双峰驼粪便中分离筛选到1株能够降解纤维素的纤维素分解菌;采用形态学观察、生理生化特性以及16S rRNA基因序列同源性分析,初步鉴定该菌株为纤维化纤维微菌(Cellulosimicrobium cellulans)。根据该菌株的产酶特性评定其产酶能力;从其发酵产纤维素酶的适宜pH、温度、时间和接种量来评价该菌株的酶学特性。结果显示,该菌株最适酶反应条件为50℃,pH为6.0,且该菌株产生的纤维素酶具有较好的热稳定性。该菌株的最佳产酶条件为接种量10%,初始pH为7.0,培养温度为30℃,发酵时间为72 h。所筛选菌株产生的酶具有一定的耐碱性和耐热性,可应用于食品行业或废料处理等方面。     

木瓜蛋白酶提取蜚蠊多糖最佳工艺研究

[目的]优化木瓜蛋白酶提取美洲大蠊多糖的工艺参数。[方法]利用不同梯度木瓜蛋白酶对美洲大蠊进行蜚蠊多糖提取试验,采用单因素和正交试验的方法,考察最佳酶用量、提取时间、温度等相关参数对提取液中多糖的含量的影响,确定蜚蠊多糖提取的工艺。[结果]试验表明,蜚蠊多糖提取的最佳条件为:酶用量为300μg/g,提取温度60℃,提取时间1.0 h。[结论]研究可为建立高效、实用的蜚蠊多糖提取途径提供技术参考,同时也为美洲大蠊的保健药品及功能性食品开发提供可靠的科学依据。     

果蔬酶褐变控制的研究进展

探讨了酶褐变的原理 ,以典型易褐变的果蔬为例 ,说明酶褐变的研究进展。论述了控制酶褐变的方法 ,加热、调节 p H值、二氧化硫及亚硫酸盐处理、驱除氧气、避免金属离子的干扰、基质络合法、新型抗氧化剂的使用、钙处理及基因遗传工程的应用等     

不同梨果实褐变特异性分析

以黄金梨、大香水、新梨七号为试材,研究了贮藏后梨褐变不同部位酚类物质含量和种类、多酚氧化酶(PPO)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)的活性及可溶性蛋白的关系。结果表明,梨果实中的酚类物质以绿原酸为主,果实褐变与酚类物质含量和多酚氧化酶活性,特别是二者在果实中不同部位的分布特性有关。黄金梨果心与其他部位比较具有较高的酚类物质含量和PPO活性。由果皮至果心CAT活性依次降低,而果皮中POD活性极大地高于其他部位。SOD的活性与褐变的直接关系不明显。     

NAD-IDH亚基1基因在油菜花粉与种子发育过程中的表达规律

以甘蓝型油菜不同发育时期的花粉与种子为材料,开展了有关NAD-IDH亚基1基因表达规律的研究。结果表明,不同发育时期花粉与种子的NAD-IDH比活力均比叶片的高。花粉与种子发育过程中NAD-IDH比活力均呈抛物线状变化,这与亚基1基因的RNA定量斑点杂交和定量RT-PCR揭示的花粉与种子发育过程中NAD-IDH亚基1基因mRNA量的变化规律完     

Environmental conditions rather than microbial inoculum composition determine the bacterial composition,microbial biomass and enzymatic activity of reconstructed soil microbial communities

The composition of microbial communities and the level of enzymatic activity in the soil are both important indicators of soil quality, but the mechanisms by which a soil bacterial community is generated and maintained are not yet fully understood. Two soil samples were collected from the same location, but each had been subjected to a different long-term fertilization treatment and was characterized by different microbial diversity, biomass and physicochemical properties. These samples were γ-sterilized and swap inoculated. Non-sterilized soil samples along with sterilized and inoculated soil samples were incubated for eight months before their nutrient content, microbial biomass, enzymatic activity and bacterial composition were analyzed. Total phosphorus, and potassium concentrations along with the overall organic matter content of the non-sterilized soil were all equal to those of the same soil that had been sterilized and self/swap inoculated. Additionally, the microbial biomass carbon concentration was not affected by the specific inoculum and varied only by soil type. The activities of catalase, invertase, urease, protease, acid phosphatase and phytase were smaller in the sterilized soils that had been inoculated with organisms from chemical fertilizer amended soil (NPK) when compared to sterilized soil inoculated with organisms from manure and chemical fertilizer amended soil (NPKM) and non-sterilized soil samples. Bacterial 16S rRNA examined by 454-pyrosequencing revealed that the composition of bacterial community reconstructed by immigrant microbial inoculum in the soil was mainly influenced by its physicochemical properties, although the microbial inoculum contained different abundances of bacterial taxa. For example, the pH of the soil was the dominant factor in reconstructing a new bacterial community. Taken together, these results demonstrated that both soil microbial composition and functionality were primarily determined by soil properties rather than the microbial inoculum, which contributed to our understanding of how soil microbial communities are generated and maintained.