Isolation and characterization of carotenoid producing bacteria from gut of Indian oil sardine Sardinella longiceps (Valenciennes, 1847)

Abstract

In the present study, screening of bacteria from gut of Indian oil sardine Sardinella longiceps collected from Kanyakumari coast, Tamil Nadu, India, has led to the isolation of a yellow pigmented strain SR-G1. Cell morphology, motility and the occurrence of spores were examined by phase contrast microscopy. The isolate was Gram-positive, with irregular rods, nonmotile branched cocci with colonies on nutrient agar yellow, opaque, glistening, circular and low convex with entire margin. The pH of the medium and incubation temperature were found to be limiting factors in growth of the bacterial strain. The optimum temperature for growth was 28 degree celsius. Key biochemical reactions include positive for catalase and negative for oxidase. The strain was H 2S-producing, starch and gelatinhydrolyzing and alkali-tolerant. The isolate grew well in minimal media containing glucose, fructose and sucrose. The strain SR-G1 was identified as Microbacterium esteraromaticum based on the phenotypic characteristics and 16S rRNA sequence analysis. Extraction and separation of the bacterial carotenoid was carried out by a one step methanol of hexane extraction. The coloured supernatant in hexane solvent was analyzed by using UV- Visible Spectrophotometer from 350-550 nm range for detecting the lambda max . The bacterial pigment was identified using a combination of UV/visible spectral data and HPLC retention time as Neoxanthin. Neoxanthin is one of the major xanthophylls which are reported to be directly associated with reduction in the risk of cancers, cardiovascular disease, agerelated macular degeneration, and cataract formation. Hence, the potential of microbial producers as an alternative to chemical synthesis of xanthophylls could be further examined.