Isolation and characterization of thermostable alkaline bacteria with ligninolytic potential

Abstract

Thermus thermophilus ST and S42 were isolated from high pH (9) and temperature (70°C) hot springs in the Alvord Desert, Oregon and the Heart Lake Geyser Basin in Yellowstone National Park, Wyoming, respectively. The two strains exhibited lignin degrading potential at pH 9 and 70°C, due to their ability to utilize the lignocellulose degradation products kraft lignin, ferulic acid, cinnamic acid, and p-coumaric acid for growth. Growth on the soluble fraction of alkaline pretreated lignocellulose sources, corn stover, corn cob and lodgepole pine was evaluated. The two isolates grew to higher cell yields due of the presence of kraft lignin, corn stover and lodge pole pine when supplemented with glucose. Dye decolorizing activity was confirmed with Remazol Brilliant Blue R (RBBR), an industrial dye and lignin analog compound. Laccase mediated 2,2' azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) activity was observed for both isolates when 0.05 mM CuSO 4 was supplemented to the growth medium. Ligninolytic bacteria capable of growth at pH 9 and 70°C are potentially useful with alkaline lignocellulose pretreatment methods to depolymerize and remove lignin prior to the production of second generation biofuel.