Bioprospecting Agarase-producing Microorganisms: Isolation and Characterization

Abstract

Background: Agarase-producing microorganisms are commonly investigated in marine environments, whereas terrestrial soils remain comparatively underexplored.  Aims: To isolate and characterise agarase-producing microorganisms from terrestrial soil samples, and to assess their agarolytic potential as an underexplored alternative to marine-derived agarase producers. Study Design: A laboratory-based isolation and biochemical characterisation study. Place and Duration of Study: Department of Microbiology, Bharati Vidyapeeth’s Matoshri Bayabai Shripatrao Kadam Mahavidyalaya, Kadegaon, and Department of Microbiology, Mahila Mahavidyalaya, Karad. [Duration of study: 3 years]. Methodology: Soil samples were collected from agricultural and forest sites and processed by serial dilution plating on modified Czapek-Dox agar, with agar as the sole carbon source. An iodine-based plate assay was used to screen for extracellular agarase activity, and positive isolates were characterised by colony morphology, Gram staining, motility testing, endospore staining, and a standard biochemical test panel. Results: Three morphotypes with extracellular agarase activity were recovered. A white colony produced the most pronounced hydrolysis zone, with an enzymatic index (EI) of 3.2. It was identified as a Gram-positive, motile, endospore-forming rod, positive for citrate and arginine utilisation, catalase, oxidase, urease, gelatin hydrolysis, casein hydrolysis, starch hydrolysis, and the Voges–Proskauer reaction, and negative for nitrate reduction, indole production, the methyl red test, and fermentation of glucose, sucrose, and mannitol. These traits place the isolate within the genus Bacillus, most closely resembling Bacillus megaterium. Conclusion: Terrestrial soil harbours agarase-producing Bacillus strains with agarolytic activity comparable to marine-derived isolates, supporting continued study of soil as a source of agarase-producing bacteria for polysaccharide bioconversion applications.