果胶分解菌的简便筛选方法

使用含０．２％果胶为唯一碳源的果胶琼脂培养基分离培养果胶分解菌株，待菌落形成后，加入０．２％刚果红水溶液染色４ｈ，在菌落周围出现绛红色水解圈者即为果胶分解菌。此法可用于果胶分解菌的筛选和计数。     

大麻韧皮果胶分解菌株的分离与鉴定

用海水和清水对大麻纤维进行浸泡处理,9d后浸泡液用梯度稀释至体积分数为0·01%,然后涂布在培养基平板上,经培养、分离、纯化,挑选数量优势的单个菌落。分别得到1309和2508这2种具有较强果胶分解能力的菌株,这2个菌株均呈革兰氏阴性,菌株1309有数根极毛运动的直杆菌,菌株2508为单极毛运动的端圆直杆菌。通过Biolog分析,初步确定菌株1309和2508分别属于假单胞菌和寡养单胞菌属的嗜麦芽寡养单胞菌。     

β-葡聚糖提取过程中果胶类物质分解

在碱法提取β-葡聚糖过程中,酒精沉淀β-葡聚糖工艺中有大量果胶一同沉淀下来,降低β-葡聚糖纯度。该实验采用添加果胶酶方法除去果胶,实验以西藏青稞和燕麦为原料,经过碱法粗提β-葡聚糖,然后调节pH,加入果胶酶溶液,在一定温度下反应一段时间,反应液浓缩后经酒精沉淀,沉淀物即为较纯β-葡聚糖。实验中研究不同pH、温度、酶加量及反应时间对酶解β-葡聚糖中果胶影响,确定酶解果胶最佳条件为：pH=3;温度为50℃;酶加量为120 U/g;反应时间为5 h;添加果胶酶使燕麦和青稞中β-葡聚糖提取率分别从0．1%和0．2%提高到1．9%和2．2%;利用粘度法测得青稞中提取β-葡聚糖分子量为1．8×10~4,燕麦中提取β-葡聚糖分子量为2．1×10~4。     

β-葡聚糖提取过程中果胶类物质分解的研究

在碱法提取β-葡聚糖的过程中,酒精沉淀β-葡聚糖工艺中有大量果胶一同沉淀下来,降低了β-葡聚糖的纯度。实验采用添加果胶酶的方法除去果胶,以西藏青稞和燕麦为原料,经过碱法粗提β-葡聚糖,然后调节pH,加入果胶酶溶液,在一定温度下反应一段时间,反应液浓缩后经酒精沉淀,沉淀物即为较纯的β-葡聚糖。实验中研究了不同的pH、温度、酶加量以及反应时间对酶解β-葡聚糖中果胶的影响,确定了酶解果胶的最佳条件为pH3、温度为50℃、酶加量为120U/g、反应时间为5h。添加果胶酶使燕麦和青稞中β-葡聚糖的提取率分别从0.1%和0.2%提高到1.9%和2.2%。利用黏度法测得青稞中提取的β-葡聚糖分子量为1.8×104,燕麦中提取的β-葡聚糖分子量为2.1×104。     

甜菜废丝中果胶的分离及特性

采用不同的溶剂分离法从甜菜废丝中提取果胶。最佳的盐酸萃取法(HCl)可从原料中提取出19.53%的果胶。HCl分离的果胶含有81.8%的半乳糖醛酸。各种方法提取的甜菜废丝果胶都有高含量的甲氧基(≥60%程度的甲基化)。果胶中还含有10—17.5%的中性糖,据气相色谱分析,其主要为阿拉伯糖和半乳糖。用凝胶渗透作用测定果胶分子量的峰值为35,500～44,700道尔顿。该果胶的持水性高、粘度低。     

醋酸菌的分离及苹果醋饮料的研制

从敞口发酵的果醋醇中分离一菌ＳＭＹ,初步鉴定为醋酸菌。利用果胶酶液化,并经澄清处理的苹果汁,调糖,酸后接种酿酒酵母,２５℃发酵７天,酒精含量达７．５％,然后接种醋酸菌ＳＭＹ,３０℃,ｒｐｍ发酵５天,乙酸含量达６．４％。在此基础上将苹果醋进行适当调配,制订出苹果醋饮料生产的工艺路线。     

从白蚁中分离筛选纤维素分解菌及其产酶性质

以羧甲基纤维素钠(CMC-Na)为惟一碳源对白蚁悬液进行富集培养,并从中分离菌株32株,通过纤维素刚果红初筛平板获得透明圈较大的8株菌,在此基础上进行摇瓶复筛,得到1株酶活较高的菌株(B3).同时对其酶促反应温度、稳定性及其酶作用底物进行了测定.结果表明:CMCase的最适酶促反应温度为50 ℃,且在该温度下有较强的稳定性,保温30 min酶活基本保持不变,60 min酶活损失约14%,菌株B3所产纤维素酶对玉米秸秆纤维素粉有较强的水解能力,同时对滤纸和脱脂棉也有一定的降解能力.     

果胶酶液体发酵条件与分离纯化的研究

果胶酶在工业生产中应用比较广泛主要由微生物发酵生产.本实验通过液体摇瓶发酵,采用氧化法测定酶活性,研究不同条件对曲霉发酵果胶酶的影响.采用盐析及有机质沉淀等方法分离酶蛋白.结果表明最适发酵培养基的组成(g/L):蔗糖20,KNP320,硫酸镁5,硫酸钙5,磷酸二氢钾5,橘子粉碎物30;适宜的发酵条件为初始pH 2.0,发酵温度22℃,250 mL摇瓶的装液量为90mL,发酵时间51 h,果胶酶活性可以达到11.40U/mL.经过试验比较,发现通过丙酮沉淀得到的果胶酶相酶蛋白比活力较高,可以达到1170.4U/mg.     

7 种天然发酵水果中醋酸菌的分离鉴定及其发酵特性

为筛选适合发酵果醋的优良醋酸菌,对苹果、草莓、香瓜、芒果、杏、樱桃、百香果7种天然发酵水果中的菌株进行分离,并采用生理生化试验、16S rDNA基因序列分析进行鉴定,对筛选鉴定的菌株进行耐乙醇、耐温、耐酸的发酵特性研究。结果表明,共分离得到29株菌落较大的菌株,经6 d发酵,筛选出产酸量大于30 g/L的菌株8株,并成功鉴定出8株醋酸菌。其中N8、Y21、A12、T11、C7为热带醋酸杆菌（Acetobacter tropicalis）,Y11和M8为塞内加尔醋杆菌（Acetobacter senegalensi）,S21为可可豆醋酸杆菌（Acetobacter fabarum）。N8、A12、T11、Y21在乙醇浓度为4%时,产酸量比其他菌株和醋酸菌AS1.41（商业菌株）高,最高可达到36.36 g/L。当温度为39℃时,这4株醋酸菌的产酸量也能达到10 g/L以上,能够耐受40 g/L的乙酸含量。结果表明N8、A12、T11、Y21具有良好的发酵产酸能力。     

芦荟中分离提取果胶的研究

本文探讨了用酸提醇沉淀法从芦荟中提取果胶的工艺条件,通过在不同提取条件下测定果胶的提取量,得出用酸提醇沉淀法从芦荟中提取果胶的最佳工艺条件.     

Isolation, characterization and identification of polyhydroxyalkanoate-accumulating bacteria from activated sludge

Two novel gram-positive bacteria capable of accumulating poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [poly(3HB-co-3HV)] were isolated from an anaerobic-oxic activated sludge system fed with acetate. Strains Lpha5 and Lpha7 are motile cocci, 1-2 microm in diameter, occurring singly or in pairs. These isolates have doubling times ranging from 0.4-1.7 d and can accumulate in high levels of poly(3HB-co-3HV) (up to 44.7% of cell dry weight) when grown on complex media. Furthermore, these two strains exhibited the rapid substrate uptake and accumulation of storage granules as observed in situ. Under aerobic conditions, about 14.4% (cell dry weight) polyhydroxyalkanoate and 82% (carbon dry weight) cellular carbohydrate were produced from acetate and glucose, respectively. Under anaerobic conditions, poly(3HB-co-3HV) and cellular carbohydrate accumulated when glucose but not acetate was fed. The result of analysis of 16S rRNA sequence revealed that both strains belong to the gram-positive high-G + C group, but are significantly different from their closest phylogenetic relatives, Dermatophilus sp. and Terrabacter sp., to warrant classification as a new species.     

Isolation and characterization of styrene metabolism genes from styrene-assimilating soil bacteria Rhodococcus sp. ST-5 and ST-10

Styrene metabolism genes were isolated from styrene-assimilating bacteria Rhodococcus sp. ST-5 and ST-10. Strain ST-5 had a gene cluster containing four open reading frames which encoded styrene degradation enzymes. The genes showed high similarity to styABCD of Pseudomonas sp. Y2. On the other hand, strain ST-10 had only two genes which encoded styrene monooxygenase and flavin oxidoreductase (styAB). Escherichia coli transformants possessing the sty genes of strains ST-5 and ST-10 produced (S)-styrene oxide from styrene, indicating that these genes function as styrene degradation enzymes. Metabolite analysis by resting-cell reaction with gas chromatography-mass spectrometry revealed that strain ST-5 converts styrene to phenylacetaldehyde via styrene oxide by styrene oxide isomerase (styC) reaction. On the other hand, strain ST-10 lacked this enzyme, and thus accumulated styrene oxide as an intermediate. HPLC analysis showed that styrene oxide was spontaneously isomerized to phenylacetaldehyde by chemical reaction. The produced phenylacetaldehyde was converted to phenylacetic acid (PAA) in strain ST-10 as well as in strain ST-5. Furthermore, phenylacetic acid was converted to phenylacetyl-CoA by the catalysis of phenylacetate-CoA ligase in strains ST-5 and ST-10. This study proposes possible styrene metabolism pathways in Rhodococcus sp. strains ST-5 and ST-10.     

Isolation and characterization of folate-producing bacteria from oat bran and rye flakes

The aim of this research was to identify endogenous bacteria in commercial oat bran and rye flake products in order to study their folate production capability while maintaining the soluble dietary fibre components in physiologically active, unhydrolyzed form.Fourty-two bacteria were isolated from three different oat bran products and 26 bacteria from one rye flake consumer product. The bacteria were tentatively identified by sequence analysis of the 16S rRNA genes. The identification results revealed up to 18 distinct bacterial species belonging to 13 genera in oat bran, and 11 species belonging to 10 genera in rye flakes. The most common bacterial genus in oat bran was Pantoea, followed by Acinetobacter, Bacillus, and Staphylococcus. Pantoea species dominated also in rye flakes. The extracellular enzymatic activities of the isolates were studied by substrate hydrolysis plate assays. Nearly 80% of the isolates hydrolyzed carboxymethylcellulose, whereas starch-degrading activities were surprisingly rare (10%). Beta-glucan was hydrolyzed by 19% of the isolates. Protease, lipase or xylanase activity was expressed by 24%, 29%, and 16%, respectively, of the isolates. Representatives of the genera Bacillus, Curtobacterium, Pedobacter, and Sanguibacter showed the highest diversity of enzymatic activities, whereas members of Janthinobacterium and Staphylococcus possessed no hydrolytic activities for the substrates studied. Production capability for total folates was analyzed from aerobic cell cultures at the stationary growth phase. The amount of folates was determined separately for the cell mass and the supernatant by microbiological assay. For comparison, folate production was also examined in a number of common lactic acid bacteria. The best producers in oat bran belonged to the genera Bacillus, Janthinobacterium, Pantoea, and Pseudomonas, and those in rye flakes to Chryseobacterium, Erwinia, Plantibacter, and Pseudomonas. Supernatant folate contents were high for Bacillus, Erwinia, Janthinobacterium, Pseudomonas, and Sanguibacter. Compared to the endogenous bacteria, lactic acid bacteria were poor folate producers. The results of this work provide the first insight into the potential role of endogenous microflora in modulating the nutrient levels of oat and rye based cereal products, and pave way to future innovations of nutritionally improved cereal foods.     

腌渍食品亚硝酸盐降解菌的分离、鉴定及其降解特性

从腌渍豆酱、香肠、腌渍萝卜中分离到5株乳酸菌,根据形态和生理生化特征等对分离到的菌株进行初步鉴定,并研究了分离菌株的生理学性质和降解特性.初步鉴定表明,L1,L3,L4和L5菌株为明串珠菌,L2菌株为链球菌.L2菌株最适生长温度为30 ℃,L1,L3,L4和L5菌株最适生长温度为25 ℃,5个菌株的最适生长pH值均为6.5,在4%～6% NaCl溶液中均能正常生长繁殖.L2菌株在30 ℃时对亚硝酸钠的降解率最高,其他菌株在25 ℃时最高;5个菌株均在pH=3.5时对亚硝酸钠的降解率最高.在适宜pH值和培养温度下,L3和L5菌株对亚硝酸钠的降解率超过93%,具有较大的应用价值.     

Isolation and characterization of thermo-acidophilic endospore-forming bacteria from the concentrated apple juice-processing environment

Forty-five thermo-acidophilic, spore-forming bacteria were isolated from a concentrated apple juice-processing environment. All of them were Gram-positive, rod shaped, and strictly aerobic that most likely belong to the genus of Alicyclobacillus. A fast identification method-16S rDNA PCR-RFLP was used to identify them. The results indicated that at the similarity level of 87%, apple juice isolates strains of 1-4 and 1-2-4 clustered with the reference strain of A. acidoterrstris DSM 3922T, and 4-2-1, S-22 and 5-1 with A. cycloheptanicus DSM 4006T, respectively. The other tested strains were different from all the reference strains in this study and may be new species of Alicyclobacillus genus or the other. In order to confirm this conclusion, we selected 7 16S rDNA PCR-RFLP identified strains and 5 type strains of Alicyclobacillus genus, carried on 51 kinds of phenotypic characteristics and analysis the data by unweighted pair group method with arithmetic mean (UPGMA). The results showed that the similarity degree between every two strains was lower than 80%. It also suggested that they may be different from each other and the unidentified strains may be new species. In addition, spoilage effects of them on 12 Brix apple juice were also studied. The result suggested that all 19 tested bacterial strains caused apple juice to become turbid, form a precipitate and off odor at varying rates when incubated at 37 degrees C up to 12 days. It suggested that these bacteria are associated with the spoilage of apple juice during storage.     

桔子果酒酵母的分离筛选

从腐烂桔子中分离得到35株酿酒酵母,从中筛选出3株发酵性能较优良的菌株.编号为F16菌株在发酵性能及桔子酒的品质方面,总体表现最优,可作为桔子酒发酵用菌种或桔子酒专用菌种选育的出发菌株.     

广东客家黄酒中乳酸菌分离鉴定与菌株特性研究

该试验对广东客家黄酒中的乳酸菌分离鉴定及对菌株特性进行了研究。从黄酒酒曲与发酵酒醪中分离纯化得到两株乳酸菌A与E。通过对菌株的形态学、生理生化、分子生物学鉴定可知,A菌与植物乳杆菌（Lactobacillus plantarum）、E菌与戊糖乳杆菌（Lactobacillus pentosus）的16S rDNA序列的亲缘性高达99%～100%。对菌株A与E特性研究结果显示,两菌株的产酸能力都很强,A菌pH达到3.8,E菌达到3.6,稍强于A菌;菌株A和E的最适生长pH值为4～6,两菌株的生长随着糖浓度的增加而受到抑制,并在乙醇含量为6%时,受到强大的抑制作用,此时E菌OD600 nm值为0.430,而A菌达到生长延缓期的OD600 nm值0.328,A菌较E菌更敏感。     

Isolation and molecular characterization of antibiotic-resistant lactic acid bacteria from poultry and swine meat products

The transfer via the food chain from animals to humans of microbes that are resistant to antimicrobial agents is of increasing concern. To determine the contributions of nonpathogenic microflora to the occurrence and spread of antibiotic resistance (AR) genes in the food chain, 123 lactic acid bacteria were isolated from 29 samples of raw and processed pork and chicken meat products that had previously tested positive for one or more AR genes that encode clinically relevant ARs: tet(M), tet(O), tet(K), erm(A), erm(B), erm(C), aac (6')-Ie aph (2")-Ia, mecA, and blaZ. All of the isolates were initially tested for their AR gene profiles by PCR. The 59 isolates carrying a tet, erm, or blaZ gene were taken through molecular identification, analyzed by determination of the MIC, and subjected to genetic fingerprinting. Lactococcus garvieae was the predominant species (28 isolates), followed by Lactobacillus plantarum (11 isolates) and L. salivarius (6 isolates), whereas Lactococcus lactis subsp. lactis, Lactobacillus johnsonii, L. reuteri, L. crispatus, and L. brevis were identified at lower frequencies. The tet(M) and erm(B) genes were the most frequently detected. Assessment of multiple resistances in 18 tet positive (tet+) isolates revealed that tet(M) plus erm(B) and tet(K) plus erm(B) were the most frequent AR gene patterns. Partial sequencing of the tet(M) open reading frame of three selected strains showed high sequence similarities (> 99%) with tet(M) genes previously found in human pathogens (Listeria monocytogenes and Neisseria meningitidis). Southern hybridization with plasmid profiles revealed these strains contained tet(M)-carrying plasmids.     

Isolation and characterization of CO2-fixing hydrogen-oxidizing marine bacteria

A CO2-fixing bacterium, strain YN-1, that can fix CO2 under chemoautotrophic conditions but not photoautotrophic conditions was isolated from seawater. Identification of the isolate was carried out using biochemical tests and 16S rDNA sequence analysis, and its characteristics were investigated. From the results of partial 16S rDNA sequence analysis, strain YN-1 showed low identity with previously reported hydrogen-oxidizing bacteria, Hydrogenovibrio marinus MH-110 and Hydrogenophilus thermoluteolus. This result indicates that strain YN-1 may be a new hydrogen-oxidizing marine bacterium. Strain YN-1 showed considerable CO2 fixation ability during continuous cultivation even at high CO2 concentration. Strain YN-1 used H2 and CO2 as energy and carbon sources, respectively. Growth characteristics were examined in batch and continuous cultivation with a view to improving the CO2 fixation rate. The results showed that CO2 fixation occurred in the absence of a light source and that the strain exhibited good growth at high CO2 concentration (40%). On the other hand, the dry cell weight was 13.4 g/l following continuous cultivation for 76 h in 10% CO2 (0.1 l/min), and at that time the amount of fixed CO2 was 18.08 g CO2/l. This indicates that strain YN-1 can efficiently fix CO2 even at high CO2 concentrations, which would allow its application to the removal of industrially discharged CO2.     

哈萨克传统发酵食品中乳酸菌的分离鉴定及代谢特性研究

采用纯培养方法从哈萨克传统发酵骆驼奶、马奶子和奶酪中分离得到11株乳酸菌。通过16S rRNA基因序列和phe S基因序列系统发育学分析,并结合形态特征和生理生化特性,确定这些乳酸菌的分类学地位。通过测定乳酸菌的耐酸耐盐特性、产酸特性、降解亚硝酸盐能力、氨基酸脱羧酶活力及抑菌能力,筛选得到了3株具有潜在生产应用价值的乳酸菌,即Lactobacillus paracasei KCH3(CICC 6277),Lactobacillus fermentum KM1(CICC 6278)和Lactobacillus fermentum KC3(CICC 6290),为果蔬发酵应用奠定了菌种基础。