Purification and characterization of a proteinase from Lactobacillus Plantarum DPC2739

The Radical-Scavenging Activity of a Purified and Sequenced Peptide from Lactic Acid Fermentation of Thunnus albacares By-Products

Yellowfin tuna by-products (Thunnus albacares) were processed to produce radical-scavenging peptides from hydrolysis by lactic acid fermentation (LAF) with Lactobacillus plantarum, papaya fruit (Carica papaya), and molasses as a carbon source for 72 h. A 15-kDa peptide was purified; after de novo sequencing, it was determined that fragments are rich in hydrophobic and neutral amino acids. The results suggest this effect is mainly to the hydrophobicity of the amino acids in their sequence. Further work is on progress to assess the ability of peptides to provide stability in lipids or in other types of samples sensitive to the action of free radicals.

Evaluation of Peanut Flour Fermented with Lactic Acid Bacteria as a Probiotic Food

The aim of this study was to evaluate the probiotic value of peanut flour fermented with lactic acid bacteria in vitro and in vivo. Four strains including Lactobacillus delbrueckii LD09, Lactobacillus casei LC35, Lactobacillus acidophilus LA51, and Lactobacillus plantarum P9 were screened for their growth and survival in peanut flour. Among all the strains, L. plantarum P9 grew to the highest cell population (9.48 log cfu/g) in peanut flour after 72 h fermentation at 37°C. After 28 days storage at 4°C, no marked change in the viable count of this strain was observed. Peanut flour fermented with L. plantarum P9 could also increase the content of crude protein and the degree of protein hydrolysis. In an in vitro system, the addition of protein from the fermented peanut flour greatly enhanced the survival of L. plantarum P9 in simulated gastric and bile juices. In vivo studies, supplementation with the fermented peanut flour in the diet of mice increased significantly the number of lactobacilli in the fecal samples compared to the control group. At the same time, the number of enterobacteria decreased significantly. These results indicated that peanut flour fermented with L. plantarum P9 strain could be a novel type of probiotic food.

Purification and characterization of a proteinase from the probiotic Lactobacillus rhamnosus OXY

A proteinase produced by the human gastrointestinal isolate Lactobacillus rhamnosus strain OXY was identified and characterized. The prtR2 gene coding for proteinase activity was detected in the examined strain. The PCR primers used were constructed on the basis of the sequence of the prtR2 proteinase gene from Lactobacillus rhamnosus GG. The enzyme was purified by fast protein liquid chromatography (FPLC) using CM-Sepharose Fast Flow and Sephacryl S-300 columns. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the enzyme had a relatively low molecular mass of 60 kD. Protease activity was observed at a pH range from 6.5 to 7.5 with optimum k(cat)/K(m) values at pH 7.0 and 40°C. Maximum proteolytic activity (59 U mL(-1)) was achieved after 48 hr of cultivation. The activity of the enzyme was inhibited only by irreversible inhibitors specific for serine proteinases (PMSF and 3,4-dichloro-isocumarine), suggesting that the enzyme was a serine proteinase. Proteinase activity was increased by Ca(2+) and Mg(2+), and inhibited by Cu(2+), Zn(2+), Cd(2+), and Fe(2+).