Cellulase-Free Xylanase by Halococcus thailandensis GUMFAS7 and Halorubrum saccharovorum GUMFAS1—Bionts of a Sponge Cinachyrella cavernosa

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Intertidal sponges, during tidal flux and filter feeding cycle, often get exposed to an influx of water of varying salinities containing halophilic microbes and suspended agricultural detritus. Microbes get established in the lumen of the host during its filter feeding process and might participate in the degradation of incoming particulate matter. We successfully isolated two haloarchaeal bionts, strains GUMFAS1 and GUMFAS7, producing cellulase-free xylanases from one such sponge, identified as Cinachyrella cavernosa inhabiting the intertidal rocky region of Anjuna, Goa-India. The bionts exhibited 4.791 and 8.714 U/mg of cellulase-free xylanase activity, respectively. Xylanase from GUMFAS7 (XS7) showed maximum activity at 37°C, pH 5 and 20% NaCl concentration. Zymographic analysis of XS7 revealed a presence of three bands with xylanase activity of molecular weight 238, 60, and 18 kDa, respectively. The strains were identified by 16S rRNA gene sequencing as Halococcus thailandensis (GUMFAS7) and Halorubrum saccharovorum (GUMFAS1). The latter was identical to another isolate obtained from the waters surrounding the host. These findings reflect a unique type of interaction between haloarchaea and sponge. An in-depth study on this cellulase-free xylanase is underway and expected to be of significance in the field of extremozymes.