Depolymerization of lignocellulose of oil palm empty fruit bunch by thermophilic microorganisms from tropical climate

•Indigenous thermophilic bacteria strains were isolated from oil palm plantation.•No additional carbon sources used in alkali lignin degradation by isolates.•Alkali lignin reduced approximately 50% by Stenotrophomonas sp. S2.•Alkali lignin reduced approximately 20% by B. subtilis S11Y.•Silica bodies of OPEFB was removed after 7 days of incubation. Previous studies on screening of lignin-degrading bacteria mainly focused on the ligninolytic ability of the isolated bacteria for the utilization of lignin monomers. In this study, we focused on the depolymerization of alkali lignin to prove the ability of the isolated thermophilic bacterial strains to utilize and depolymerize more than a monomer of alkali lignin within 7 days of incubation. Indigenous thermophilic bacterial isolates from the palm oil plantation were used to evaluate the depolymerization and utilization of alkali lignin. The confirmation of the bacterium-mediated depolymerization of oil palm empty fruit bunch was achieved through the removal of silica bodies, as observed with scanning electron microscopy. Stenotrophomonas sp. S2 and Bacillus subtilis S11Y were able to reduce approximately 50% and 20% of alkali lignin at 7 days of incubation without the requirement for additional carbon sources.