Abstract This study investigated the effect of Lactobacillus isolated from Chinese fermented food on antibiotic-induced intestinal microflora disorder during the early life of mice. The experimental strain Lactobacillus fermentum (LF) CQPC04 was isolated from naturally fermented pickles in Chongqing, China. Lactobacillus plantarum (LP) KFY02 was isolated from naturally fermented yogurt from Korla in the Xinjiang Uygur Autonomous Region. The results showed that LF-CQPC04 and LP-KFY02 alleviated the decrease in bacterial diversity caused by the antibiotics, maintained the abundance of beneficial bacteria, and reduced the abundance of harmful bacteria. These results suggest that LF-CQPC04 and LP-KFY02 can be used as probiotics to alleviate antibiotic-induced intestinal microfloral disorder. antibioticinduced antibiotic induced mice LF (LF CQPC CQPC0 Chongqing China LP (LP KFY KFY0 Region LFCQPC04 LFCQPC LF-CQPC0 LPKFY02 LPKFY LP-KFY0 antibiotics bacteria LFCQPC0 LF-CQPC LPKFY0 LP-KFY

Abstract The milk-clotting enzyme (MCE) produced by Bacillus amyloliquefaciens GSBa-1 achieved the scale-up criterion from 0.25-L erlenmeyer flask to 5-L bioreactor sucessfully and exhibited remarkable milk-clotting activity (MCA) (626.3 SU/mL) that was 1.45-fold higher than the control by optimizing both medium composition and fermentation conditions.The growth of GSBa-1 was optimized through response surface methodology employing Plackett-Burman design and Box-Behnken design. The final optimized fermentation conditions were as follows: maltose (7.258g/L), corn steep liquor (8.15g/L), and Tween 80 (1.97g/L); constant fermentation pH (7.0), temperature (45 °C) and stirrer speed (200 rpm). Kinetic models of microbial growth (X), product formation (P), and substrate consumption (S) were constructed, respectively. The derived model was the first reported model for GSBa-1 rennet production, contributing visual description for the rennet fermentation process, as well as the improvement of its productivity and efficiency.

Abstract In this study, the exopolysaccharides (EPSs)-producing L. plantarum YW11 was initially evaluated for its tolerance to simulated artificial gastric juice and bile salts, and cell surface hydrophobicity. Subsequent study using a HT-29 tumor-burdened nude mouse model showed that the EPS had potent immunomodulatory and antitumor activities. Administration of the EPS had no influence on body weight of the mice, and it could significantly prevent HT-29 tumor cells induced acute liver and kidney damages. The purified EPS at a dose of 5 mg/mL was able to enhance effectively the killing activities of splenic natural killer cells and cytotoxic T lymphocyte, and to stimulate the secretion of serum cytokines IL-2 and TNF-α. As evidenced by a cell culture assay, the EPS exhibited obvious inhibition on growth of colon cancer HT-29 cells treated with 600 μg/mL of the EPS for 72 h with an inhibition rate of 58.02%. Administration of the EPS obviously inhibited growth of HT-29 xenograft tumor to an extent near that of the positive control (5-Fu, 25 mg/kg bw). Therefore, the results of this study indicated the important roles of the EPS in the potential probiotic functions of the strain.

ABSTRACT Lactobacillus plantarum strains have been extensively used in food processing and preservation. L. plantarum also has the potential to convert polyunsaturated fatty acids, e.g. linoleic acid (LA) into bioactive and less toxic fatty acid metabolites. The objective of this study was to assess the capability of probiotic L. plantarum 13-3 to convert Linoleic Acid (LA) to different fatty acid metabolites in the medium supplemented with differential concentrations of LA, and the relevant reactions were characterized by in silico calculation. L. plantarum 13-3 was grown in MRS medium containing LA from 1% to 10%, and the fatty acid metabolites formed in the medium were identified and quantitated by GC-MS and in silico studies were done to confirm the enzymatic reactions involved in its conversion. The results showed that L. plantarum 13-3 could convert LA at different concentrations to 5 different fatty acid metabolites i.e, (Z)-Ethyl heptadec-9-enoate, 9,12-Octadecadienoic acid (Z, Z), methyl ester, Octadec-9-enoic acid, cis-11,14-Eicosadienoic acid, methyl ester and (Z)-18-Octadec-9-enolide. Among these metabolites, the formation of an long chain fatty acid Octadec-9-enoic Acid, also known as 18:1, N-9 or Delta(9)-Octadecenoic acid, is classified as a member of the Long-chain fatty acids in media supplemented with 4% to 10% LA, is being reported for the first time. Putative candidate enzymes involved in biotransformation of LA into fatty acid metabolites were identified in whole genome of L. plantarum 13-3, sequenced previously. In silico studies confirmed that several enzymes including the linoleate isomerase, acetoacetate decarboxylase and oxidoreductase may be involved in biotransformation of LA into fatty acid metabolites. These enzymes could effectively bind the LA molecule mainly by forming hydrogen bonding between the acidic groups of LA and the proline residues at the active sites of the enzymes validating the putative reacting partners.

To analyze the exopolysaccharide (EPS) production by Streptococcus thermophilus ST1, cultures were cultivated in 10% (w/v) reconstituted skim milk under different growth conditions including various temperatures and pHs of growth medium, supplementation of the medium with various carbon sources (glucose, lactose, sucrose, galactose and fructose) and nitrogen source (whey protein concentrate, or WPC). The results showed that most EPS production by strain ST1 was obtained at a temperature (42°C) and pH (6.5) optimal for its growth. Supplementation of the skim milk medium with either carbohydrates or WPC increased both growth and polymer formation by different extents, with sucrose being most effective among the carbon sources tested. Under the optimal cultural conditions, i.e. pH 6.5, 42°C with 2% (w/v) sucrose and 0.5% (w/v) WPC, 135.80 mg l-1 of EPS was produced by strain ST1. The monosaccharide composition of the EPS was determined to be glucose and galactose (2:1), and the molecular mass of the EPS was 3.97 × 10(6) Da. The aqueous solution of the EPS at 1% (w/v) showed relatively high viscosity, indicating the potential of this EPS-producing S. thermophilus strain for applications in the improvement of physical properties of fermented milk products.