短乳杆菌(Lactobacillus brevis)去除亚硝酸盐的研究

短乳杆菌有较强去除亚硝酸盐能力，亚硝酸盐含量在250mg／L以内，接种短乳杆菌48h亚硝酸盐全部去除。短乳杆菌处理亚硝酸盐主要处于亚硝酸还原酶还原亚硝酸盐阶段。短乳杆菌去除亚硝酸盐的最适pH值为5．0～6．0，最适温度为30℃；在其它条件不变的情况下，发酵初期(10～26h)亚硝酸盐去除量随接种量的增加而增加，最适接种量为5％。亚硝酸盐含量在200mg／L以内，短乳杆菌对亚硝酸盐的去除量与底物浓度有极显著的线性关系。  

Analysis of S-layer proteins of Lactobacillus brevis

Abstract The presence of S-layer proteins in Lactobacillus brevis was examined by SDS-PAGE analysis. Thirty six out of a total of 41 L. brevis strains possessed S-layer proteins of molecular masses ranging from 38 to 55 kDa. Western blot analysis using antisera raised against whole cells of S-layer protein-carrying strains demonstrated the heterogeneity of L. brevis S-layer proteins. No clear relationship was observed between the presence of S-layer proteins or their immunological characteristics and the physiological activity of L. brevis as a beer spoilage organism.  

Purification and partial gene sequence of the tyrosine decarboxylase of Lactobacillus brevis IOEB 9809

Some lactic acid bacteria contain a tyrosine decarboxylase (TDC) which converts tyrosine to tyramine, a biogenic amine frequently encountered in fermented food and wine. Purification and microsequencing of the TDC of Lactobacillus brevis IOEB 9809 allowed us to determine a partial sequence of the TDC gene encoding 264 amino acids of the enzyme. Analysis of this protein sequence revealed typical features of pyridoxal phosphate-dependent amino acid decarboxylases while not any known decarboxylase was closely related to the TDC of L. brevis IOEB 9809. In addition, we could detect other L. brevis strains carrying a TDC gene in a rapid assay based on the polymerase chain reaction.  

亚硝酸盐影响Lactobacillus brevis 4903发酵的研究

通过研究可知,亚硝酸盐对Lactobacillusbrevis4903发酵有抑制作用,环境中亚硝酸盐一旦分解掉,这种抑制作用就会被解除。分析其原因:①亚硝酸盐抑制了乳酸菌生长,从而抑制了乳酸发酵;②在发酵初期可能因亚硝酸盐还原酶的作用,使亚硝酸盐酶解生成NH3,NH3中和了乳酸菌生成的酸(H ),从而使环境pH值的下降和酸的积累变得缓慢。  

一株短乳杆菌所产细菌素的部分特性

为了研究分离自内蒙古传统发酵乳制品——"焦克"的短乳杆菌KLDS1.0373所产细菌素的部分生物学特性(抑菌谱,对酶、pH和温度的敏感性,作用方式)。短乳杆菌KLDS1.0373发酵液经硫酸铵沉淀和葡聚糖凝胶纯化后,测定其部分生物学特性,并采用Tricine-SDS-PAGE方法确定细菌素的分子量范围。结果表明:短乳杆菌KLDS1.0373所产细菌素的抑菌活性对热和pH不敏感,在100°C或121°C处理30 min后抑菌活力略有增强,可被多种蛋白酶失活,但对α-淀粉酶不敏感。该细菌素分子量约为3.8 kD,对多种革兰氏阳性和阴性菌有抑制作用,作用方式为杀菌。  

horC confers beer-spoilage ability on hop-sensitive Lactobacillus brevis ABBC45cc

AIMS: To determine whether horC confers beer-spoilage ability and to evaluate the validity of horC as a trans-species genetic marker for differentiating the beer-spoilage ability of lactic acid bacteria (LAB). METHODS AND RESULTS: Hop-sensitive Lactobacillus brevis ABBC45cc was transformed with an expression plasmid, pHYchorBC, containing putative multidrug resistance gene horC and its putative regulator horB, and the transformant was designated as ABBC45cc/pHYchorBC. As a control, ABBC45cc was transformed with pHYchorB that contains horB, and the transformed strain was designated as ABBC45cc/pHYchorB. As a result of beer-spoilage assay of these transformants, ABBC45cc/pHYchorBC exhibited beer-spoilage ability, whereas ABBC45cc/pHYchorB did not. Furthermore ABBC45cc/pHYchorBC showed higher hop resistance than ABBC45cc/pHYchorB, accounting for the differences in beer-spoilage ability observed between the two transformants. ABBC45cc/pHYchorBC also exhibited higher resistance to various structurally unrelated drugs, compared with ABBC45cc/pHYchorB. CONCLUSIONS: horC was shown to confer hop resistance and beer-spoilage ability on ABBC45cc by presumably encoding a multidrug transporter. SIGNIFICANCE AND IMPACT OF THE STUDY: The finding that horC plays an important role in hop resistance and beer-spoilage ability supports the validity of horC as a trans-species genetic marker for differentiating the beer-spoilage ability of LAB.  

Atomic resolution structures of R-specific alcohol dehydrogenase from Lactobacillus brevis provide the structural bases of its substrate and cosubstrate specificity

The R-specific alcohol dehydrogenase (RADH) from Lactobacillus brevis is an NADP-dependent, homotetrameric member of the extended enzyme family of short-chain dehydrogenases/reductases (SDR) with a high biotechnological application potential. Its preferred in vitro substrates are prochiral ketones like acetophenone with almost invariably a small methyl group as one substituent and a bulky (often aromatic) moiety as the other. On the basis of an atomic-resolution structure of wild-type RADH in complex with NADP and acetophenone, we designed the mutant RADH-G37D, which should possess an improved cosubstrate specificity profile for biotechnological purposes, namely, a preference for NAD rather than NADP. Comparative kinetic measurements with wild-type and mutant RADH showed that this aim was achieved. To characterize the successful mutant structurally, we determined several, partly atomic-resolution, crystal structures of RADH-G37D both as an apo-enzyme and as ternary complex with NAD or NADH and phenylethanol. The increased affinity of RADH-G37D for NAD(H) depends on an interaction between the adenosine ribose moiety of NAD and the inserted aspartate side-chain. A structural comparison between RADH-G37D as apo-enzyme and as a part of a ternary complex revealed significant rearrangements of Ser141, Glu144, Tyr189 and Met205 in the vicinity of the active site. This plasticity contributes to generate a small hydrophobic pocket for the methyl group typical for RADH substrates, and a hydrophobic coat for the second, more variable and often aromatic, substituent. Around Ser141 we even found alternative conformations in the backbone. A structural adaptability in this region, which we describe here for the first time for an SDR enzyme, is probably functionally important, because it concerns Ser142, a member of the highly conserved catalytic tetrad typical for SDR enzymes. Moreover, it affects an extended proton relay system that has been identified recently as a critical element for the catalytic mechanism in SDR enzymes.  

Comparative analysis of conserved genetic markers and adjacent DNA regions identified in beer-spoilage lactic acid bacteria

AIMS: To conduct an inter-species comparative study on the nucleotide sequences of the conserved DNA regions surrounding ORF5, a genetic marker for differentiating beer-spoilage lactic acid bacteria. METHODS AND RESULTS: The conserved DNA regions surrounding ORF5 were examined by PCR analysis, using three beer-spoilage strains, Lactobacillus brevis ABBC45C, L. paracollinoides LA2T and Pediococcus damnosus ABBC478. As a result, the DNA regions containing ORF1-7, originally found in ABBC45C, appeared to be conserved among the three strains, while the downstream region was not found in L. paracollinoides LA2T and P. damnosus ABBC478. The sequencing analysis of the conserved DNA regions of LA2T and ABBC478 revealed ca 99% nucleotide sequence identities with that of ABBC45C. CONCLUSIONS: The nucleotide sequences of the ca 8.2 kb DNA regions containing ORF1-7 were virtually identical among the three strains belonging to different species. The internal organizations of the ORFs were found to be remarkably similar. SIGNIFICANCE AND IMPACT OF THE STUDY: The level of nucleotide sequence identities suggests the DNA regions surrounding ORF5 were horizontally acquired by these beer-spoilage strains belonging to the three different species of lactic acid bacteria.