Low-Carbohydrate Tolerant LAB Strains Identified from Rumen Fluid: Investigation of Probiotic Activity and Legume Silage Fermentation.

Palaniselvam Kuppusamy,Jeong Sung Jung,Dahye Kim,Ki Choon Choi,Ilavenil Soundharrajan,Hyung Soo Park,Seung Hak Yang

doi:10.3390/microorganisms8071044

Abstract

The objective of this study was to isolate and characterize lactic acid bacteria (LAB) with low carbohydrate tolerance from rumen fluid and to elucidate their probiotic properties and the quality of fermentation of Medicago sativa L. and Trifolium incarnatum L. silage in vitro. We isolated 39 LAB strains and screened for growth in MRS broth and a low-carbohydrate supplemented medium; among them, two strains, Lactiplantibacillus plantarum (Lactobacillus plantarum) RJ1 and Pediococcus pentosaceus S22, were able to grow faster in the low-carbohydrate medium. Both strains have promising probiotic characteristics including antagonistic activity against P. aeruginosa, E. coli, S. aureus, and E. faecalis; the ability to survive in simulated gastric-intestinal fluid; tolerance to bile salts; and proteolytic activity. Furthermore, an in vitro silage fermentation study revealed that alfalfa and crimson clover silage inoculated with RJ1 and S22 showed significantly decreased pH and an increased LAB population at the end of fermentation. Also, the highest lactic acid production was noted (p < 0.05) in LAB-inoculated silage vs. non-inoculated legume silage at high moisture. Overall, the data suggest that RJ1 and S22 could be effective strains for fermentation of legume silage.

Highlights

Lactic acid bacteria (LAB) are a heterogeneous group of Gram-positive microorganisms that have drawn attention for their probiotic potential, functionality, safety, and stability in various harsh environments
We investigated the new low-carbohydrate-tolerant LAB strains for legume silage fermentation under high moisture conditions for prolonged storage
The highest antifungal activity of RJ1 and S22 was seen in the MRS agar spot method after 48 h incubation. These results indicate that the RJ1 LAB strain had the highest antifungal effect against A. fumigatus, A. niger, and P. roqueforti, with a zone of inhibition of 24.5 ± 0.35, 21.33 ± 0.15, and 14.56 ± 0.33 mm, respectively

Summary

Introduction

Lactic acid bacteria (LAB) are a heterogeneous group of Gram-positive microorganisms that have drawn attention for their probiotic potential, functionality, safety, and stability in various harsh environments. LAB isolated from animal sources, such as rumen fluid, feces, and forages, has been shown to improve silage fermentation These isolates have high mass, fast growth rates, good adhesion activities, and a high survival percentage in acidic and alkaline environments [5]. Lactiplantibacillus plantarum ( known as Lactobacillus plantarum) and Pediococcus pentosaceus are important homo-fermentative starter cultures used in the food and beverage industry to enhance the quality of products and restrict the growth of harmful microbes. The advantage of these LAB inoculants is that they do not adversely affect animal health, productivity, or safety [7,8]

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