Application of Marine Bacteria Associated with Seaweed, Ulva lactuca, for Degradation of Algal Waste

Abstract

In the present study, three marine Ulva lactuca-associated bacteria capable of producing agarase, λ-carrageenase, amylase, cellulase and protease were isolated from rocky intertidal region of Anjuna beach, Goa, India, and designated as DM1, DM5 and DM15. Based on 16S rRNA sequence analysis and biochemical tests, bacteria were identified as Vibrio brasiliensis, Bacillus subtilis and Pseudomonas aeruginosa. Bacteria DM1, DM5 and DM 15 could able to utilize seaweed waste (Sargassum powder) in seawater-based media by releasing reducing sugars, 503.3 ± 17.5 µg/ml, 491.6 ± 20 µg/ml and 376.6 ± 16 µg/ml, respectively, which was confirmed through 3,5-dinitrosalicylic acid method. Therefore, the eco-friendly reuse of seaweed waste is possible by using marine bacteria for the production of reducing sugars in ethanol-producing industry. All three bacterial isolates were found to produce indole acetic acid (IAA) at concentration 98 ± 12 µg/ml, 113.6 ± 13 µg/ml and 121.6 ± 8.5 µg/ml, respectively. Nitrogen fixation by bacterial strains was confirmed when they showed growth on artificial seawater devoid of nitrogen and comprising of 5% carrageenan as a sole source of carbon and gelling agent. Photosynthetic seaweed, Ulva lactuca, provides organic carbon and O2 for associated bacteria and associated bacteria fix atmospheric N2 and provides iron by siderophore production and synthesize hormone IAA for algal growth during their cooperative association.