Bioprospecting for alginate-lyase producing microorganisms for brown seaweed bioprocessing

Abstract Enzymes can play an important role in environmentally friendly processing of seaweed biomass, and there is a rich diversity of microbes that may harbour seaweed specific polysaccharide-lyases. In the context of alginate bearing brown seaweed, wild-type alginate lyase (AL) producing microbes would be useful for alginate-related bioprocesses. Eight microorganisms capable of extracellular AL production were isolated and identified up to genus level using 16S and ITS sequencing. Seven of these microbes are bacteria of the genera, Bacillus sp (4/8), Pantoea sp. (1/8), Lysinibacillus sp. (1/8), Stappia sp. (1/8), and a yeast of the genus Rhodotorula sp. (1/8). Through employing a screening approach in different media, isolates were evaluated for their capacity to produce AL, and three isolates were selected from the genera Bacillus sp., Lysinibacillus sp., and Rhodotorula sp. for displaying high relative AL activity among the candidate isolates. In addition, a preliminary medium was identified which contained two nitrogen sources (peptone and yeast extract) at a ratio of 5:1 and the highest salt concentration of all media tested. This medium may be utilised as a starting point for development of similar bioprocesses in the future. Importantly, the Rhodotorula sp. isolated in this study potentially marks the first report of these yeasts displaying AL activity, rendering this a valuable strain for future kelp valorisation practices. Moreover, this study identified three microbes which were confirmed to produce high levels of AL: two bacterial strains (a Bacillus sp., which is of a genus that is widely employed in bioprocessing, and a lesser known Lysinibacillus sp.), and a Rhodotorula sp. yeast, which is of a versatile genera that could also produce other valuable products.