Isolation, identification and characterization of Lactobacillus species diversity from Meekiri: traditional fermented buffalo milk gels in Sri Lanka

A.M.M.U Adikari,Hasitha Priyashantha,J.N.K Disanayaka,D.V Jayatileka,S.P Kodithuwakku,J.A.M.S Jayatilake,J.K Vidanarachchi

doi:10.1016/j.heliyon.2021.e08136

Abstract

Traditional fermented buffalo milk gel; Meekiri, is a popular buffalo milk-derived product in Sri Lanka. Predominantly, it is produced using the back-slopping (adding a small amount of the previous fermentate) technique, following the life-long traditions available at the cottage level. Hence, diverse and unclassified starter cultures are likely to be established across the varying geographical regions of Meekiri production. In the present study, we aimed to elucidate the diversity of lactic acid bacteria (LAB) and their characteristics including probiotic properties from major Meekeri production areas (n = 22) in Sri Lanka. Lactic acid bacteria was isolated from locally produced Meekiri samples (n = 23) and characterized based on morphological, biochemical, physiological profiles and potential of probiotic properties. The isolates revealed five different colony and cell morphologies and were classified as heterofermenters, homofermenters and facultative heterofermenters based on CO2 production using glucose. None of the isolates showed the ability to grow either at 5 °C or 0 °C, while 71 % and 100 % survival of the isolates were observed at 15 °C and 45 °C, respectively. Amplified ribosomal DNA restriction analysis (ARDRA) primarily grouped the isolates into three distinct clusters based on their DNA banding patterns. Subsequently, 16S rRNA sequencing of isolates revealed the presence of four species namely, Limosilactobacillus fermentum (n = 18), Latilactobacillus curvatus (n = 2), Lactobacillus acidophilus (n = 2) and Lactiplantibacillus plantarum (n = 1) and in the phylogenetic analysis, it was represented by four distinctive clades. All the isolated species demonstrated promising probiotic potential with antibiotic sensitivity, antimicrobial properties, bile acid tolerance and acid tolerance. In conclusion, traditional back-slopping Meekiri in Sri Lanka contains diverse LAB, with a negligible geographical variation at species-level. Our work provides a strong foundation and insights into future applications in starter culture development for the fermentation of buffalo's milk.

Highlights

Fermented buffalo milk production is popular in countries where buffalo rearing is practiced
Antibiotic sensitivity of the isolates We found all the isolated L. fermentum and L. plantarum were sensitive to the studied antibiotics, except vancomycin, while L. acidophilus and L. curvatus isolates were sensitive to all the studied antibiotics (Table 2)
L. plantarum isolated from Dadih in West Sumatra was identified with good probiotic properties given it inhibits the growth of E. coli (Abesinghe et al, 2020); such growth inhibition of E. coli was not observed in the current study and it may be a strain level differences within the same species

Summary

Introduction

Fermented buffalo milk production is popular in countries where buffalo rearing is practiced. Meekiri is a traditional fermented milk gel derived from buffalo milk in Sri Lanka. Fresh buffalo milk is heat-treated (pasteurized at around 92 C) and inoculated (inoculation rate is undefined in cottage-level production) with lactic acid bacteria (at 42 C), and incubated overnight at room temperature (~30–35 C) to achieve milk coagulation (Abesinghe et al, 2020). The popularity of using back-slopping to produce fermented buffalo milk products in rural context is mainly due to its simplicity with respect to input

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Results

Conclusion