Bioactive Metabolites of Lactiplantibacillus plantarum K014 Against Methicillin-Resistant Staphylococcus aureus ATCC43300 and In Vitro Evaluation of Its Antibacterial, Antioxidant and Anti-inflammatory Activities.

This study aims to evaluate the effects of bioactive metabolites produced by lactic acid bacteria against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. A total of six lactic acid bacteria (LAB) were selected to evaluate the antimicrobial activity against MRSA ATCC 43300, a skin pathogen that is highly resistant to most antibiotics. The K014 isolate from a fermented vegetable recorded the highest inhibition against MRSA ATCC 43300 at 91.93 ± 0.36%. 16S rRNA sequencing revealed the K014 isolate is closely related to L. plantarum and the sequence was subsequently deposited in the GenBank database with an accession number of MW180960, named as Lactiplantibacillus plantarum K014. The cell-free supernatant (CFS) of L. plantarum K014 had tolerance to high temperature as well as acidic pH. The bioactive metabolites, such as hydrogen peroxide, lactic acid and hyaluronic acid, were produced by L. plantarum K014. Result from ABTS assay showed higher antioxidant activity (46.28%) as compared to that obtained by DPPH assay (2.97%). The CFS had showed anti-inflammatory activity for lipoxygenase (LOX) assay at 43.66%. The bioactive metabolites of L. plantarum K014 showed very promising potential to be used topical skin pathogens.

Insight into the pilot-scale fed-batch fermentation for production of Enterococcus faecium CW3801 using molasses-based medium.

Enterococcus sp. has been used as starters in food fermentation due to their probiotic and antimicrobial properties in food biopreservation. The antimicrobial properties were mainly contributed by the bacteriocin called enterocin. Hence, the availability of a cost-effective pilot-scale cultivation conditions is a necessity for the production of probiotic bacteria. This study aims to investigate optimization of medium composition using sugarcane molasses as a carbon source using response surface methodology and the potential use of fed-batch cultivation for improvement of the cell viability of Enterococcus faecium CW3801 for the use as a probiotic starter culture. Two feeding strategies (ramp and constant) were applied in fed-batch cultivation for enhancement of the production of E. faecium in a 2-L stirred tank bioreactor using the optimized medium and scaled up to a 15-L bioreactor. Optimized fermentation medium which comprised of 10% (v/v) of molasses and 10 g/L of yeast extract at pH 7 yielded maximum cell viability of 29.4 × 1011 CFU/mL with 3900 AU/mL of bacteriocin-like inhibitory substances (BLIS) activity. In the fed-batch, the cell viability (8.4 × 1013) and dry cell weight (6.34 g/L) reached the highest in optimized medium when the ramp (stepwise) feeding was applied. In scaling up to 15-L bioreactor, the growth of E. faecium was achieved at 2.3 × 1013 CFU/mL with the dry cell weight of 5.28 g/L under the same condition. The BLIS in 15-L bioreactor was 6% higher than the 2-L bioreactor. This study demonstrated that molasses and yeast extract are good feedstock for the growth of E. faecium. The E. faecium, a non-vancomycin resistant enterococcus (VRE) was successfully produced by a fed-batch cultivation approach and scaled up to a 15-L bioreactor using a ramp feeding strategy. Results from this study revealed that the fed-batch cultivation using molasses-based medium has industrial potential for the production of probiotics.

Influence of freeze-drying and spray-drying preservation methods on survivability rate of different types of protectants encapsulated Lactobacillus acidophilus FTDC 3081.

The aims of this study were to compare the effectiveness of different drying methods and to investigate the effects of adding a series of individual protectant such as skim milk, sucrose, maltodextrin, and corn starch for preserving Lactobacillus acidophilus FTDC 3081 cells during spray and freeze-drying and storage at different temperatures. Results showed a remarkable high survival rate of 70-80% immediately after spray- and freeze-drying in which the cell viability retained at the range of 109 to 1010 CFU/mL. After a month of storage, maltodextrin showed higher protective ability on both spray- and freeze-dried cells as compared to other protective agents at 4°C, 25°C, and 40°C. A complete loss in viability of spray-dried L. acidophilus FTDC 3081 was observed after a month at 40°C in the absence of protective agent.