Isolation and screening of carotenoid-producing Bacillus spp. from seashore saline soil and seawater at Hon Son islet

Abstract

Carotenoids are natural pigment compounds with a variety of colors. They are antioxidants and boost the immune system. It is interesting to examine strains of bacteria capable of producing carotenoids applied in the food industry, animal feed, and aquaculture. Rach Gia bay of Kien Giang province has a good ecosystem, and the carotenoid-producing microorganisms in these regions are very plentiful. However, there are fewer studies about them in this region. This study was conducted to isolate and select carotenoids-producing Bacillus from Hon Son islet of Rach Gia bay. Seashore saline soil and seawater samples were shocked at 65°C in 1 hour and plated on Difco sporulation medium. Colored colonies of bacteria were selected and incubated at 37°C on Difco sporulation medium. Pigments from these isolates were extracted in the mixture of methanol and chloroform (with the ratio 1:2 of v/v). The extracted solutions were scanned absorbance by spectrophotometer at the wavelength range from 400 to 600 nm. Bacterial isolates were identified by 16S rRNA sequencing. Twenty carotenoid-producing bacterial species were isolated, including five colony colors such as pale yellow, yellow, yellow-orange, pale pink, and pink. They were Gram-positive, positive-catalase test, motile, and endospore-forming. The results of extracted solutions from 20 bacterial species indicate that all the extracts have absorbance from 400-600 nm, this is the popular absorbance of carotenoids. Two high-carotenoid-producing species (HS3-7 and HS8-3) were analyzed the 16S rRNA gene sequence. They were showed high similarity with Bacillus vietnamensis species Marseille-P799 and Bacillus infantis species NRRL B-14911, respectively.