Isolation of a novel strain of Lactic Acid Bacteria from traditionally fermented common lime (Citrus aurantifolia) of Assam, India and analysis of exopolymeric substances produced by the strain

Abstract

1 common lime (Citrus aurantifolia) of Assam, India and analysis of exopolymeric 2 substances produced by the strain. 3 4 5 Abstract 28 29 A gram positive, rod shaped and catalase negative strain of Lactic Acid Bacteria was isolated 30 from traditionally fermented common lime (Citrus aurantifolia) of Assam, North-East India. 31 Bacterial identification was done by using conventional morphological and biochemical 32 methods as well as advanced molecular technique. Traditionally fermented lime juice was 33 serially diluted on selective culture medium and growth of translucent, ropy bacterial colony 34 was observed in the culture plate. Isolated bacteria were identified up to species level by 35 using ribosomal RNA (rRNA) gene sequencing technique. Based on nucleotide homology 36 and phylogenetic analysis the isolate was found to be a strain of Lactobacillus delbrueckii. 37 This is the first report of finding this sub species of Lactic Acid Bacteria in citrus fruit 38 product. The sequence determined in this study has been deposited in the GenBank database 39 with sequential accession number KT198973. The bacterial isolate also produced 40 exopolysaccharide when grown in chemically defined medium. Fourier Transform Infrared 41 Spectroscopy (FTIR) was done for chemical and compositional characterization of partially 42 purified exopolysaccharide. 43 44 Introduction: 50 Lactic acid bacteria (LAB) are one of the most important groups among bacteria due to the 51 "generally recognized as safe (GRAS)" status of this group and their products. The members 52 of this group are mainly characterised for the formation of lactic acid as a final product of the 53 carbohydrate metabolism [1, 2]. The possibility of Lactic acid bacteria in the field of health 54 and nutrition is humongous and this can boast up different sections of traditional treatments. 55 The evidence that LAB can stimulate the immune system is astounding and captivating and 56 opens numerous research areas regarding mechanisms and effective utilization[3]. One of the 57 important aspect of using LAB derived products comprises its cost affectivity as these 58 products can be produced without much difficulty and sophisticated instruments. They have 59 moderately low level of toxicity contrasted with other microbial products [4]. The growing 60 concerns about health and well-being, along with an interest in consuming natural foods, 61 have given probiotics a unique position in the food market. There are lot of documented 62 works with regard to the presence of Lactic acid bacteria in dairy products and for long they 63 are being used extensively as starter culture[5]. However, research had rarely been centered 64 on the microflora found in fermented fruits for the presence of this specific group of bacteria 65 although the microenvironment and nutritive profile of fruits which are rich in nutrients are 66 quite conducive for such bacteria to multiply[6]. Ong et al. reported enterococcus type of 67 LAB in fermented red dragon fruit juice [7]. These bacteria were al...