Phenotypic Characterisation and Molecular Identification of Potentially Probiotic Lactobacillus sp. Isolated from Fermented Rice

Abstract

Fermented rice is known as a healthy food due to the presence of lactic acid bacteria. The study was carried out to identify and characterise the lactic acid bacteria (LAB) from white and red fermented rice Bg (Bathalagoda) varieties. Fermentation was carried out naturally by soaking red, white, raw, and cooked rice in sterile distilled water (1:3) overnight at 27 °C in an earthen pot. Potentially probiotic bacterial were isolated and the species of the isolated lactic acid bacteria were confirmed based on 16S rDNA gene sequencing and were studied for phenotypic characteristics, including morphological, physiological (growth temperature, salt tolerance, milk coagulation), and biochemical (carbohydrate fermentation pattern) characteristics, using API 50CH kits. Distinct clusters of cocci (48), diplococci (30), and rod-shaped bacteria (30) were observed in fermented rice. Five species of lactic acid bacteria were identified, including Latilactobacillus curvatus GRLb1, 2, 10, and 11 (the predominant Bacillus species); Latilactobacillus graminis GRLb 8; Limosilactobacillus fermentum GRLb17; Weissella confuse GRLb4; and Pediococcus pentosaceus GRLc1. The base pair length of amplified DNA for the isolates was 1500 Bp. Most of the isolates were able to grow at temperatures ranging from 10 °C to 45 °C, tolerate up to 6.5% salt, and coagulate milk with homofermentative characteristics. The beneficial physiological and biochemical properties of isolated Lactobacillus species from fermented rice revealed their potential applications in the food industry. The similar species of bacteria that were isolated from different sources show their probiotic characteristics. Further studies are recommended to confirm their probiotic properties and health benefits.