Physiology of Sporolactobacillus strains isolated from different habitats and the indication of in vitro antagonism against Bacillus species

Environmentally Friendly Production of D(-) Lactic Acid by Sporolactobacillus nakayamae: Investigation of Fermentation Parameters and Fed-Batch Strategies

The interest in the production of lactic acid has increased due to its wide range of applications. In the present study, the variables that affect fermentative D(−) lactic acid production were investigated: neutralizing agents, pH, temperature, inoculum percentage, agitation, and concentration of the medium components. An experimental design was applied to determine the optimal concentrations of the medium components and fermentation was studied using different feeding strategies. High production (122.41 g/L) and productivity (3.65 g/L·h) were efficiently achieved by Sporolactobacillus nakayamae in 54 h using a multipulse fed-batch technique with an initial medium containing 35 g/L of yeast extract (byproduct of alcohol production), 60 g/L of crystallized sugar, and 7.5 mL/L of salts. The fermentation process was conducted at 35°C and pH 6.0 controlled by NaOH with a 20% volume of inoculum and agitation at 125 rpm. The production of a high optically pure concentration of D(−) lactic acid combined with an environmentally friendly NaOH-based process demonstrates that S. nakayamae is a promising strain for D(−) lactic acid production.

Sporolactobacillus vineae sp. nov., a spore-forming lactic acid bacterium isolated from vineyard soil

Two spore-forming, facultatively anaerobic, lactic acid bacteria, strains SL153(T) and SL1153, were isolated from vineyard soil in Korea. Cells of both strains were slightly curved, Gram-positive, motile rods that measured between 1 and 4 mum in length and were approximately 0.5 mum in diameter. Strains SL153(T) and SL1153 fermented glucose, fructose, mannose and sorbitol, but were negative for nitrate reduction, catalase and oxidase. The predominant cellular fatty acids of the two isolates were iso-C(15 : 0), anteiso-C(15 : 0) and anteiso-C(17 : 0). meso-Diaminopimelic acid, glucose, mannose and galactose were determined in their whole-cell hydrolysates. 16S rRNA gene sequences from the two strains were almost identical (99.9 %) and they could be placed in the genus Sporolactobacillus according to phylogenetic analysis. The species most closely related to SL153(T) were Sporolactobacillus inulinus and Sporolactobacillus terrae with 16S rRNA gene similarities of 95.7 and 95.5 %, respectively, with the type strains. Levels of DNA-DNA relatedness between strain SL153(T) and the type strains of S. inulinus, S. terrae and Sporolactobacillus kofuensis were 18.5, 18.0 and 17.0 %, respectively. On the basis of the phylogenetic (16S rRNA gene), chemotaxonomic and phenotypic evidence given in this study, it is proposed that strains SL153(T) and SL1153 should be assigned to the genus Sporolactobacillus as representatives of the novel species Sporolactobacillus vineae sp. nov. The type strain is SL153(T) (=KCTC 5376(T)=JCM 14637(T)).

Basic Characteristics of Sporolactobacillus inulinus BCRC 14647 for Potential Probiotic Properties

The basic characteristics of the spore-forming lactic acid bacterium, Sporolactobacillus inulinus BCRC 14647, was evaluated in vitro for its potential probiotic properties. Assessments including acid and bile salt tolerance, adhesiveness, and antagonistic effects on pathogenic Salmonella enteritidis BCRC 10744, as well as inhibition factors of spent culture supernatant (SCS) and an invasion assay, were conducted using Lactobacillus acidophilus BCRC 10695 and two bifidobacteria (Bifidobacterium bifidum BCRC 14615 and B. longum BCRC 11847) as a reference. In the results, S. inulinus spores presented significantly higher survival rates than the vegetative cell form in acidic conditions as well as the reference bifidobacteria. However, L. acidophilus showed the highest viability among all tested strains. Similar results were found in the bile tolerance test. Compared with the reference strains, the vegetative cell form of S. inulinus possessed a proper adhesive characteristic (71.7 bacteria/field for S. inulinus and 91.3 and 45.7 bacteria/field for B. bifidum and B. longum, respectively). In the adhesion assay, both the spore form of S. inulinus (17.1 bacteria/field) and the negative control, L. bulgaricus BCRC 14009 (5.9 bacteria/field), displayed nonadhesive traits. The vegetative cells of S. inulinus and its SCS both dramatically decrease the adhesion of S. enteritidis to Caco-2 cells; meanwhile, the SCS of S. inulinus vegetative cells inhibited the growth of S. enteritidis in the inhibition zone test. The existing inhibition factor could be assumed to be lactic acid in the SCS. From the results of the invasion assay, S. inulinus showed high safety properties. In conclusion, based on these in vitro evaluations, results suggest that S. inulinus presents probiotic features of great potential in the vegetative cell form.

H2-Producing bacterial communities from a heat-treated soil inoculum

Hydrogen gas (approximately 60% H(2)) was produced in a continuous flow bioreactor inoculated with heat-treated soil, and fed synthetic wastewater containing glucose (9.5 g l(-1)). The pH in the bioreactor was maintained at 5.5 to inhibit consumption of H(2) by methanogens. The objective of this study was to characterize bacterial communities in the reactor operated under two different hydraulic retention times (HRTs of 30-h and 10-h) and temperatures (30 degrees C and 37 degrees C). At 30-h HRT, the H(2) production rate was 80 ml h(-1) and yield was 0.91 mol H(2)/mol glucose. At 10-h HRT, the H(2) production rate was more than 5 times higher at 436 ml h(-1), and yield was 1.61 mol H(2)/mol glucose. Samples were removed from the reactor under steady-state conditions for PCR-based detection of bacterial populations by ribosomal intergenic spacer analysis (RISA). Populations detected at 30-h HRT were more diverse than at 10-h HRT and included representatives of Bacillaceae, Clostridiaceae, and Enterobacteriaceae. At 10-h HRT, only Clostridiaceae were detected. When the temperature of the 10-h HRT reactor was increased from 30 degrees C to 37 degrees C, the steady-state H(2) production rate increased slightly to 463 ml h(-1) and yield was 1.8 mol H(2)/mol glucose. Compared to 30 degrees C, RISA fingerprints at 37 degrees C from the 10-h HRT bioreactor exhibited a clear shift from populations related to Clostridium acidisoli (subcluster Ic) to populations related to Clostridium acetobutylicum (subcluster Ib).

Acid and bile tolerance of spore-forming lactic acid bacteria

Criteria for screening probiotics such as bile tolerance and resistance to acids were studied with 13 spore-forming lactic acid producing bacteria. Different strains of Sporolactobacillus, Bacillus laevolacticus, Bacillus racemilacticus and Bacillus coagulans grown in MRS broth were subjected to low pH conditions (2, 2.5 and 3) and increasing bile concentrations. Among these microorganisms, Bacillus laevolacticus DSM 6475 and all Sporolactobacillus strains tested except Sporolactobacillus racemicus IAM 12395, were resistant to pH 3. Only Bacillus racemilacticus and Bacillus coagulans strains were tolerant to bile concentrations over 0.3% (w/v).

Biological preservation of foods with reference to protective cultures, bacteriocins and food-grade enzymes

A review is presented on the present status of biological preservation of foods. Recent developments are discussed with respect to underlying mechanisms of inhibition by 'protective' cultures, and special reference is made to lactic acid bacteria (LAB) and their 'food-grade' safety. The role of bacteriocins, their limitations and potentiating role in biological systems, is also addressed. The use of enzymes (e.g. lysozyme) for food preservation is mainly restricted by economic factors, their inactivation by endogenous food components and their limited activity spectrum. Practical applications of protective cultures refer to particular food commodities that either constitute novel systems with respect to packaging and/or composition, or represent special hygienic risks. It is concluded that biological preservation cannot substitute GMP; it, however, offers an additional (and acceptable) processing parameter for improving the safety and assuring the quality of a given food.