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Pigment is the most attractive attribute and integral part of human life. The source of the pigment used for different applications is chemically synthesised. However, pigment produced from natural sources (such as plants and microorganisms) can also be applied as a coloring agent. In addition to being colorants, many natural pigments are also fascinating bioactive substances with possible health benefits. Agrochemicals, food, medicine, pharmacology, cosmetics, and numerous other industries use these compounds. In this study, a total of 7 pigmented colonies were isolated from the soil samples of different areas of Assam. Out of 7 pigmented colonies, 3 colonies showed orange color and 4 colonies showed yellow color. Based on the similarity of growth pattern and high intensity of pigmentation one colony from each pigment was picked for further studies. The isolated orange and yellow pigments were denoted as S1 and S2, respectively. With the help of Bergey’s Manual of Determinative Bacteriology the isolated pigmented strains were preliminary identified based on their morphological, microscopic, and biochemical characteristics and after that 16S rRNA gene sequencing helped to identify the bacteria at the species level and the strains were identified as (S1) Micrococcus aloeverae ON377368 and (S2) Exiguobacterium aestuarii ON377409. The identified strains Micrococcus aloeverae and Exiguobacterium aestuarii showed a high pigment production rate at specific optimized conditions such as at temperature 37°C, pH 6, and NaCl concentrations at 1.5-2% and strains also showed a good characteristic growth pattern at a specific time interval. Therefore, the present study may be a helpful step towards the large-scale manufacture of pigments and the extraction, purification, and characterization of the pigment extracted from these strains will lead to provide a potent eco-friendly natural dye in the industrial sector.

In this review, the relevance of diversity of yeasts and their interactive association in household ethnic fermentation are discussed. The longstanding traditional household fermentation practice involves preparation of fermented product such as alcoholic beverages from various indigenous agricultural products with the help of microorganisms cultivated from local environment and perpetuated for hundreds of years through generations indoctrinating an indigenous knowledge system. Northeast India is known for its rich physiographic and geo-demographic diversity and is home to several ethnicities who follow unique practices of household traditional fermentation. The diversity of yeasts present within the microbial inoculum used for fermentation by different indigenous communities has been keenly studied and reported to be unique in spite of their common source for starter substrates. Saccharomyces yeasts are primarily involved in alcoholic fermentation, whereas non-Saccharomyces yeasts, which are reportedly confined to a particular geographical region, have been reported to contribute toward the final outcome of fermentation produce. During fermentation, interaction among these large microbial communities and their resulting physiological expression within the fermentation micro-environment is believed to affect the final quality of the product. Mechanism of quorum sensing plays an important role in these interactions in order to maintain proportionality of different yeast populations wherein the quorum sensing molecules not only regulate population density but also effectively aid in enhancement of alcoholic fermentation. Additionally, various secondary metabolites, which are secreted as a result of inter-species interactions, have been found to affect the quality of beverages produced. This review concludes that diverse species of yeasts and their interaction within the fermentation micro-environment influence the sustainability and productivity of household ethnic fermentation.

In this investigation, growth promoting role of indole-3-acetic acid (IAA) was assessed on yeasts representing three genera and four species viz Wickerhamomyces anomalus, Saccharomyces cerevisiae, Candida tropicalis and Candida glabrata isolated from traditional fermentative starter materials of Ahom, Rabha, Bodo, Karbi, Kachari and Mishing communities of Assam, India. Isolates were first assessed for their ability to synthesize IAA in presence and absence of external tryptophan and was examined for stimulatory effect of growth on the tested isolates. Tryptophan dependent IAA synthesis was observed in 92% of isolates while 72% of isolates could synthesize IAA in absence of exogenous tryptophan. Candida glabrata KC3X could synthesize maximum IAA while Saccharomyces cerevisiae KR5.6 did not synthesize IAA in presence of external tryptophan. 3 out of 14 Wickerhamomyces isolates and the sole Saccharomyces isolate KR4.10 were found to synthesize significant amount of IAA in absence of tryptophan. Treatment of exogenous IAA on the growth of tested yeasts revealed that Saccharomyces isolates were more pronounced than others. Wickerhamomyces anomalus, Candida tropicalis and Candida glabrata did not show any significant response of growth in presence of exogenous IAA. This study concludes that plant condiments present in starter materials may aid in accelerated growth of Saccharomyces yeasts compared to non-Saccharomyces ones. Yeasts capable of synthesizing IAA but unable to show appreciable growth in presence of IAA may presumably facilitate sustenance of Saccharomyces spp. in fermentative consortia.