Antimicrobial activity of characterized Leuconostoc spp. as novel probiotics isolated from Oreochromis spp. (red tilapia) against fish pathogen Edwardsiella tarda

Aims@#This study aimed to isolate and characterize putative new probiotic with antimicrobial properties against common fish pathogens from the gut of Oreochromis spp. (red tilapia). @*Methodology and results@#A total of 28 colonies were isolated from gut of Oreochromis spp. and characterized phenotypically. Eight isolates were selected for probiotic characterization. Temperature, salinity, pH and bile salt tolerance, antibiotic susceptibility and antimicrobial test against selected fish pathogens (Aeromonas hydrophila, Edwardsiella tarda and Staphylococcus aureus subsp. aureus ATCC 25923) were conducted. Characterization studies revealed isolates suited for freshwater environment and exhibited tolerance against wide range of salinity, pH and bile salt. Isolates displayed different antibiotic susceptibility profile, with six exhibited antimicrobial properties against E. tarda. Molecular identification based on 16S rRNA gene sequencing showed 99.44%, 98.59% and 91.21% sequence similarity with Leuconostoc pseudomesenteroides strain 3832T, Leuconostoc lactis strain KCC202369T and Leuconostoc mesenteroides strain 4332T, respectively as compared to known sequence in the GenBank. When identified Leuconostoc spp. were coated on feed pellets, no major decrease in viability over 21 days of storage at 4 °C were observed, with an average of 8 log CFU/mL.@*Conclusion, significance and impact of study@#The characterized species allow further application assessment of the probiotic-supplemented tilapia feed. Host-originated Leuconostoc displayed potential antimicrobial properties against fish pathogen E. tarda. The isolates Leuconostoc is expected to provide protective effect for Oreochromis spp. against edwardsiellosis and to exert beneficial effects more efficiently as compared to commercial probiotics which are not specifically target for Oreochromis spp., thereby indirectly helping fish farmers in achieving economic sustainability and increase affordability of fish.

Submerged fermentation improves bioactivity of mulberry fruits and leaves / 中草药·英文版

Objective: Mulberry (Morus spp.) fruits and leaves have been proven to possess nutraceutical properties. Due to its fast and easy growing characteristics, mulberry fruits (MF) and leaves (ML) potentially emerge as a great source of functional foods. This study aims to enhance bioactivities (antioxidant, anti-inflammation, and hypoglycemic activity) of MF and ML via submerged fermentation using bacteria (Lactobacillus plantarum TAR 4), yeast (Baker's yeast and red yeast) and fungi (Tempeh and Tapai starter). Methods: In this study, 25% (mass to volume ratio) of MF and ML were fermented (48 h) with 1% (mass to volume ratio) of different microbial cultures, respectively. Effects of different fermentations on MF and ML were determined based on the changes of total phenolics (TPC), flavonoids (TFC), anthocyanins, total sugar, DPPH activity, ferric reducing antioxidant power (FRAP), albumin denaturation inhibition activity (ADI), anti-lipoxygenase activity and α-amylase inhibition activity (AI). Results: Generally, ML had higher AI than MF. However, MF exhibited higher DPPH, FRAP and anti-lipoxygenase activity than ML. After all forms of fermentation, DPPH and AI activity of MF and ML were increased significantly (P < 0.05). However, the effects of fermentation on TPC, FRAP, ADI and anti-lipoxygenase activity of MF were in contrast with ML. TPC, FRAP and anti-lipoxygenase activity of ML were enhanced, but reduced in MF after fermentation. Although the effects exerted by different microorganisms in MF and ML fermentation were different, the bioactivities of MF and ML were generally improved after fermentation. Fermentation by Tempeh starter enhanced TPC (by 2-fold), FRAP (by 2.3-fold), AI (at 10% increment) and anti-lipoxygenase activity (by 5-fold) of ML, whereas Tapai fermentation effectively enhanced the DPPH (at 17% increment) and ADI (by 2-fold) activity of MF. Conclusion: Findings of this study provide an insight into the future process design of MF and ML processing into novel functional foods.