Isolation and Molecular Characterization of Alginate Lyase-Producing Bacteria from South Lampung Waters, Indonesia

This study aims to isolate and identify bacteria producing alginate lyase from Sargassum sp. collected from the coastal waters of Rajabasa, South Lampung. Seaweed samples underwent a 5-day natural fermentation method prior to bacterial isolation on nutrient agar supplemented with sodium alginate. Alginate lyase activity was evaluated using the clear zone assay following 10% cetylpyridinium chloride (CPC) treatment, and positive isolates were characterized through morphological and Gram-staining observations. Molecular identification was conducted by amplifying and sequencing the 16S rRNA gene. From a total of 21 isolates obtained, 14 demonstrated alginolytic activity. Among them, isolate A6 exhibited the highest alginate lyase index (2.58±0.6) and was selected for further analysis. BLAST similarity and phylogenetic reconstruction revealed a 99.71% sequence identity with Klebsiella aerogenes. Notably, isolate A6 displayed two major peaks of enzyme activity at 24 and 96 hours, indicating distinct phases of production and identifying optimal harvesting times. This research confirms Klebsiella aerogenes as a potent alginate lyase producer from Indonesian Sargassum representing a regional novelty with strong potential for biotechnological enzyme applications.