产GABA乳酸菌的筛选鉴定及其发酵条件研究

为了筛选得到一株高产γ-氨基丁酸(γ-aminobutyric acid,GABA)的乳酸菌,本研究选取传统发酵食品作为菌株来源,采用薄层层析法和高效液相色谱法对分离出的20株乳酸菌的GABA生产能力进行定性和定量分析,并对高产菌株进行种属鉴定及产GABA影响因素研究。结果表明:从传统发酵食品中分离得到一株GABA高产菌株14#,其发酵液中GABA含量为2.30 g/L,经菌落形态、生理生化特性以及16S rDNA基因序列分析鉴定该菌株为植物乳杆菌(Lactobacillus plantarum),研究其产GABA的影响因素并确定发酵优化条件为:MRS基础发酵培养基中以15 g/L的葡萄糖作为碳源,以10 g/L的酵母粉和15 g/L的牛肉膏作为复合氮源,添加1.5% L-谷氨酸钠,接种量为4%,初始pH为6.0,37 ℃静置培养48 h。优化后GABA含量可达9.12 g/L,比优化前产量(2.30 g/L)提高了近3倍。     

产γ-氨基丁酸乳杆菌高效筛选方法的建立

本研究首先发现11株短乳杆菌皆产生大量气体导致培养管盖子弹起,进一步对48 h发酵液pH进行测定,发现有3株菌的发酵液具有较高pH,薄层层析结果表明产生大量气体且发酵液pH较高的菌株能够产生γ-氨基丁酸（GABA）,进一步通过质谱实验验证,产量分别是124.14、203.00、211.50 mg/L。通过高效测序发现11株短乳杆菌GABA合成基因簇结构和核酸序列基本相同,因此在基因层面无法实现高效筛选。根据GABA生物合成过程中产生二氧化碳及消耗氢离子的现象建立高效筛选方法。进一步对220株植物乳杆菌进行产气观察结合pH测定判定菌株是否产GABA,并通过薄层色谱进行验证,表明此方法可行。该方法具有低成本高效的特点,能够快速从大量乳杆菌中筛选出产GABA菌株。     

产GABA菌株的诱变选育及培养基优化的研究

γ-氨基丁酸是一种天然存在的非蛋白质氨基酸,具有多种对人体有益的功能。通过对一株GABA高产乳酸菌进行紫外诱变,诱变后得到1株高产GABA突变株LP-S2,GABA产量平均达到7.274g/L,比出发菌株提高了53.07%。通过连续传代遗传稳定性较好。对突变株LP-S2进行发酵培养基的优化。最终GABA最大产量达到9.703g/L。通过紫外诱变的方法,扩大了GABA产生菌来源。为发酵法生产GABA奠定了更好的基础。     

高含量GABA桑叶茶工艺优化研究

以γ-氨基丁酸(GABA)含量为评价指标,在单因素试验基础上采用L₉(3³)正交试验设计方法,研究谷氨酸钠浓度、杀青功率、杀青时间对桑叶茶GABA含量的影响,确定制作高含量GABA桑叶茶的最佳工艺。结果表明,影响GABA含量的主要因素依次为谷氨酸钠浓度、杀青时间、杀青功率;经正交试验后确定最佳工艺参数为谷氨酸钠浓度5%、杀青功率210 W、杀青时间2 min,在此工艺下GABA含量最高为10.81 mg/g,同时还提高了1-脱氧野尻霉素(DNJ)的含量。     

乳酸菌SK 005发酵产GABA(γ-氨基丁酸)的条件优化

GABA(γ-氨基丁酸)是一种天然存在的功能性氨基酸,具有降低血压、改善脑功能、镇静、增强长期记忆及提高肝、肾机能等生理活性.通过对乳酸菌SK 005发酵产GABA的条件设计了一系列优化实验,得到了最佳的发酵条件.以一次回归正交设计实验,运用方差分析确定了最佳的发酵温度,发酵时间,培养基起始pH.安排五水平正交实验研究豆粕粉,玉米浆粉,酵母味素,葡萄糖,K2PHO4,MSG对发酵产GABA的影响,逐步回归法找出主要影响因子豆粕粉,玉米浆粉,MSG.利用中心组合设计与响应面分析进一步考察这三个主要影响因子,确定了最佳培养基的组成及浓度.乳酸菌SK 005发酵产GABA的优化发酵条件为发酵温度30℃,发酵时间2 d,培养基起始pH 6.8,培养基成分葡萄糖5g/L,豆粕粉21.5 g/L,玉米浆粉21.8g/L,MSG 9.5g/L,实验结果有良好的重现性,GABA产量达5.4g/L.     

GABA生产菌株（乳酸菌）的筛选

本试验以自然发酵泡菜为原料，用平板划线分离得到10株菌株，通过对菌株个体特征观察和部分生理生化特征的鉴定以及纸层析法进行定性分析、改良纸层析法与HPLC法结合的定量分析，得到产γ-氨基丁酸的优势乳酸菌B2，产量为1．18mg／ml。     

GABA(γ-氨基丁酸)的功能性

γ-氨基丁酸(GABA)富含于蔬菜、水果及发酵食品中,是日常摄取的氨基酸的一种。作为抑制性神经物质在人的大脑中枢神经系统中起作用。关于GABA的功能性,以前曾报道其具有抑制血压上升作用,但是在日常生活中摄取的GABA的量很少,所以,光从食物中很难获取能发挥其功能性的需要量。因此,我们注重研究有饮食生活经验的发酵食品中的微生物,开发了由微生物发酵的高效GABA生产技术。而且,经过一系列试验确认了GABA的有效作用,如抗压力作用等新功能。     

利用小麦胚芽制备GABA

探讨以小麦胚芽为原料,通过添加谷氨酸和吡哆素来实现γ-氨基丁酸(GABA)的生物转化,为研发食品来源的高安全性的GABA提供理论基础。以单因素实验(谷氨酸添加量、反应温度、反应时间和反应液pH)为基础,采用响应面分析法对制备GABA工艺参数进行优化,结果表明,最优反应条件为,谷氨酸添加量为80 g/L,反应液pH为5.6时,小麦胚芽中的谷氨酸脱羧酶酶活最高,并在反应温度为40℃反应4 h,最终可以生成GABA(35.42±2.19)mg/L(RSD=1.94%)。本研究建立的小麦胚芽制备GABA二次线性回归模型准确有效,优化制备工艺参数是可行的。     

γ-氨基丁酸（GABA）在食品工业中的应用研究

γ-氨基丁酸（GABA）是一种天然存在的功能性蛋白质。介绍了GABA的理化性质、生理功能及制备方法,并对其在食品工业中的应用及发展前景进行了综述与展望。     

产γ-氨基丁酸乳酸菌的筛选及发酵过程研究

从不同泡菜中筛选到6株产γ-氨基丁酸(GABA)的乳酸菌,其中A号乳酸菌产量相对较高,GABA产量为1.261 g/L。A号菌株经16S rDNA鉴定为植物乳杆菌,初步命名为Lactobacillus plantarum WZ011。通过单因素和正交设计方法对其发酵培养基进行优化,得到最佳培养基成分(g/L):葡萄糖13,酵母膏5,谷氨酸钠12,盐酸吡哆醇0.15,无水乙酸钠2,MgSO4.7H2O 0.02,MnSO4.4H2O 0.001,FeSO4.7H2O 0.001,NaCl 0.001。Lactobacillus plantarum WZ011发酵动力学曲线表明GABA的发酵过程大致分为菌体生长与产物生成2个阶段。降低培养基的氮源含量和添加盐酸吡哆醇,谷氨酸钠的利用率提高至99%且GABA生产速率提高了2倍多。优化后GABA最高产量可达5.814 g/L,比优化前提高了79%,且提前了48 h进入GABA生产稳定期。     

微生物絮凝剂产生菌的筛选鉴定

以活性污泥作为菌种来源,采用常规微生物学方法分离到76株菌株,初筛后13株菌有絮凝活性,复筛后菌株70絮凝活性最高.通过对菌株70的形态观察,生理生化试验以及16S rRNA基因序列分析,该菌鉴定为解鸟氨酸拉乌尔菌(Raoultella ornithinolytica).     

Economic comparison of divergent strains of Holstein-Friesian cows in various pasture-based production systems

The objective of this paper was to compare the economic efficiency of 3 divergent strains of Holstein-Friesian cows—high-production North American (HP), high-durability North American (HD), and New Zealand (NZ)—across a variety of Irish pasture-based production systems: Moorepark (MP), high concentrate (HC), and high stocking rate (HS). Physical performance data were obtained from a 5-yr study conducted previously. The economic performance of each strain and feed system was derived for 3 production scenarios: European Union (EU) milk quota applied at the farm level using predicted future prices and costs (S1); EU milk quota applied at the industry level, thus permitting quota leasing at predicted future prices and costs (S2); and EU milk quota applied at the industry level with a limitation on land availability (S3). The economic results showed that in a fixed milk quota scenario, the NZ strain in the MP and HS feed systems returned the highest profitability. The HD strain in the MP and HS feed systems proved the next most profitable, whereas the HP animals were least profitable in all feed systems. Similar to S1, in S2 the NZ were most profitable; however, the difference between the MP and HS was much smaller. The HP strain proved least profitable in all feed systems. In S3, the NZ strain was again most profitable; however, within that scenario the HS feed system was optimal. These results show that exclusive genetic selection for increased milk production results in reduced farm profitability because the productivity gains achieved are outweighed by associated increases in reproductive wastage costs in a pasture-based system. These results reinforce the economic value of genetic improvement based on a selection index encompassing traits of economic significance pertinent to the production environment.     

Isolation and characterization of mutants of Propionibacterium strains

Procedures were developed to isolate and characterize mutants of strains of dairy propionibacteria. These procedures included the construction of minimal defined media to support growth of the strains, optimization of conditions of exposure of the strains to nitrosoguanidine, and identification of the phenotypes of the mutants that were generated. The minimal defined medium contained inorganic salts, adenosine, three vitamins, and sodium lactate as the carbon source, with cysteine, methionine, or cysteine plus methionine added as required by some strains. For mutagenesis, cells were exposed to either 100, 200, or 1000 micrograms/ml nitrosoguanidine, depending on the sensitivity of the strain, for 60 min at 35 degrees C. At least nine stable mutants were isolated and characterized for each of the five strains under study. The most frequent mutations generated were requirements for arginine, histidine, methionine, and uracil and alteration in pigment production.     

秸秆纤维素降解菌的分离筛选、复合菌系构建及产酶条件优化

该研究采用刚果红染色法和滤纸条崩解法从山西老陈醋源中分离筛选纤维素降解菌,通过形态观察及分子生物学技术对其进行菌种鉴定。以滤纸酶活性为筛选指标构建复合菌系,采用单因素试验及响应面试验对其产酶发酵条件进行优化,并评价其对不同秸秆的降解效果。结果表明,筛选出3株纤维素降解菌,编号为J1、J2和J3,分别被鉴定为灿烂类芽胞杆菌（Paenibacillus lautus）、千叶类芽胞杆菌（Paenibacillus chibensis）和窖泥类芽胞杆菌（Paenibacillus vini）。3株菌等比例复配得到最佳复合菌系D,其最优产酶发酵条件为初始pH 7.4,接种量9%,发酵温度40℃。在此优化条件下,滤纸酶活性达到35.10 U/m L,是优化前的1.6倍。复合菌系D对不同秸秆均具有较好的降解效果,且对小麦秸秆的降解率最高,达27.63%。     

Isolation and characterization of benzene-tolerant Rhodococcus opacus strains

Twenty-two benzene-utilizing bacteria were isolated from soil samples. Among them, three isolates were highly tolerant to benzene. They grew on benzene when liquid benzene was added to the basal salt medium at 10--90% (v/v). Taxonomical analysis identified the benzene-tolerant isolates as Rhodococcus opacus. One of the benzene-tolerant isolates, designated B-4, could utilize many aromatic and aliphatic hydrocarbons including benzene, toluene, styrene, xylene, ethylbenzene, propylbenzene, n-octane and n-decane as sole sources of carbon and energy. Strain B-4 grew well in the presence of 10% (v/v) organic solvents that it was capable of using as growth substrates. Genetic analysis revealed the benzene dioxygenase pathway is involved in benzene catabolism in strain B-4. A deletion-insertion mutant defective in the benzene dioxygenase large and small subunits genes (bnz A 1 and bnz A 2) was as tolerant to organic solvents as the wild-type strain B-4, suggesting that utilization or degradation of organic solvents is not essential for the organic solvent tolerance of R. opacus B-4.     

PHA生产菌株的筛选及生长特性研究

以衡水湖湖底污泥为初始样品,经富集、分离纯化、尼罗蓝染色,远红外光谱及气相定性、定量分析筛选出具有PHA合成能力的菌株,结果表明,在分离得到的菌株中有5株菌具有PHA合成能力,其编号分别定为SJ-2、S J-5、S J-9、SJ-11、S J-20,5株菌产PHA的远红外扫描图谱相近,均在1740cm-1处有较强吸收峰,此处为PHA结构的特征峰.5株产PHA的量不同,SJ-9菌产量最高为1.85g/L,菌株SJ-9的最适生长环境为温度为28℃C、pH值8、转速150r/min、装液量100mL/500mL.     

一株产蓝色素菌株的筛选及初步鉴定

从自贡地区土壤中分离得到一株产蓝色素细菌,编号为T2013。通过形态特征观察、生理生化实验分析和全细胞脂肪酸检测以及16S r DNA比对分析,确定了该细菌为杜擀氏菌属的一种。通过系统进化树显示该细菌与菌株Duganella nigrescens strain YIM H16(EF584756)具有较高的同源性。T2013可能为新种,命名为Duganella sp.T2013。      

萘降解菌的分离、鉴定及降解特性的研究

该研究对乌梁素海水中高效萘降解菌进行筛选并分析了降解特性。筛选出8株以萘为唯一碳源和能源的萘降解菌,对其进行了形态观察、生理生化试验和16S rRNA基因序列分析。结果表明,这8株菌分别属于细杆菌属（Microbacterium）、短波单胞菌属（Brevundimonas）、红球菌属（Rhodococcus）、迪茨氏菌属（Dietzia）和假单胞菌属（Pseudomonas）。其中,菌株S2、S8、C4和C8在培养10 d内可降解88%、64%、65%和76%的质量浓度为3.5 g/L的萘。当以硝态氮为唯一氮源时,可不同程度地增加萘的降解率,微量元素和混合维生素对萘降解菌的生长及萘降解有一定的促进作用,在最适pH条件下萘降解效果较好。     

庆阳豆豉优势菌株的分离鉴定

为了确定庆阳豆豉的主要作用微生物,获得优势发酵菌株,以甘肃庆阳7个县区农户所制的发酵豆豉为材料,采用不同培养基分离纯化,通过平板透明圈法初筛,发酵液蛋白酶、纤维素酶和淀粉酶活性测定,对传统豆豉发酵微生物进行了分离筛选,最后对优势菌株进行生理生化鉴定及16S rDNA分子生物学鉴定。共分离出22株细菌菌株,初筛获得10株均可分解蛋白质、淀粉和纤维素能力的菌株,其中QY2b蛋白酶和纤维素酶活性最高,分别达到了25.37 U/mL和6.015 U/mL。通过对QY2b的形态观察及生理生化试验,结合16S rDNA鉴定手段,确定该优势发酵菌种为枯草芽孢杆菌(Bacillus subtilis)。