Abstract
The aim of the present study is to optimize the growth conditions for improved production of alkaloids by promising marine actinomycetes isolated from marine sediments collected on Kakinada coast. The bioactive compounds were extracted from the isolated actinomycetes using organic solvents and screened for alkaloids using qualitative tests. The presence of alkaloids in the crude methanolic extract was confirmed by UV spectroscopic analysis and quantified by BCG method. The effect of pH, temperature, carbon and nitrogen sources on the growth and fermentative production of alkaloids was optimized. The strain was improved for enhanced production of alkaloids by physical and chemical mutagenesis. The antimicrobial activity of the crude alkaloid extract was determined by the well diffusion method. The isolated strain exhibited the highest growth and alkaloid production at pH 6 and temperature 30oC in 7 days. The alkaloid production was significantly increased 4.5-folds with UV treatment for 30 min and further 5.5-folds with ethidium bromide treatment (30µg/mL) for 1h. The resultant double mutant strain exhibited significantly high antimicrobial activity against S.aureus compared to other bacterial strains with MIC index less than 4. The isolated double mutant strain of actinomycetes can be a potential source of antibiotic alkaloids.
Highlights
Alkaloids are naturally occurring nitrogenous basic compounds that occur in plants, microorganisms, marine organisms, and animals
Marine actinomycetes are widely recognized as industrially important microorganisms
Bioactive compounds were extracted into different solvents which differ in polarity from 21 days old starch casein broth culture of isolated marine actinomycetes
Summary
Alkaloids are naturally occurring nitrogenous basic compounds that occur in plants, microorganisms, marine organisms, and animals. The majority of these compounds display biological activity. Alkaloids become the focus of research in academia, industry and joint ventures for their development as antibacterial agents (Olusola et al, 2015). Marine bioactive alkaloids are emerging as novel leads (Urban et al, 2000). The first alkaloid isolated from marine sources is hordenine (Kasim et al, 2010). Several potent alkaloids were isolated from marine sources. Lodopyridone is a unique alkaloid isolated from marine actinomycetes collected at the mouth of the La Jolla coast (Maloney et al, 2009). A novel alkaloid with broad-spectrum of antibacterial and cytotoxic
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