Biological process effective in co-production of biohydrogen and α-amylase from CO-containing by-product gas using a hyperthermophilic archaeon

Abstract

Recently, we have reported biohydrogen production from CO-containing industrial byproduct gas using a hyperthermophilic archaeon, Thermococcus onnurineus NA11,2. In this study, in order to develop co-production process of H2 andα-amylase from CO-containing industrial byproduct gas, we constructed a mutant strain of T. onnurinues NA1, designated as 156T-AM by integrating α-amylase gene encoding mature form of α-amylase with C-terminal His6-tag into the intergenic region between TON_1126 and TON_1127 genes of the parental strain, 156T3. The 156T-AM mutant displayed higher activity of α-amylase than that of the parental strain during the growth on CO-containing medium. Final cell yield (OD600), maximum H2 production rate and maximum specific H2 production rate of 156T-AM mutant strain was similar to those of 156T strain in a bioreactor using 100% CO or syngas. After the cultivation, α-amylase could be purified by one-step metal affinity chromatography from the cell extract, and the purified protein displayed specific activity of 7500 unit mg-1. Additionally, the whole cell extract was applicable to saccharify potato peel at 80 oC and approximately 0.15 mg ml-1 reducing sugar could be generated from 5 % (V/V) potato peel waste. This study successfully demonstrated co-production of H2 and a valuable protein from CO or syngas, providing envision to develop hyperthermophilic cell factory to upcycle industrial waste gasrom CO-containing industrial byproduct gas, we constructed a mutant strain of T. onnurinues NA1, designated as 156T-AM by integrating α-amylase gene encoding mature form of α-amylase with C-terminal His6-tag into the intergenic region between TON_1126 and TON_1127 genes of the parental strain, 156T3. The 156T-AM mutant displayed higher activity of α-amylase than that of the parental strain during the growth on CO-containing medium. Final cell yield (OD600), maximum H2 production rate and maximum specific H2 production rate of 156T-AM mutant strain was similar to those of 156T strain in a bioreactor using 100% CO or syngas. After the cultivation, α-amylase could be purified by one-step metal affinity chromatography from the cell extract, and the purified protein displayed specific activity of 7500 unit mg-1. Additionally, the whole cell extract was applicable to saccharify potato peel at 80 oC and approximately 0.15 mg ml-1 reducing sugar could be generated from 5 % (V/V) potato peel waste. This study successfully demonstrated co-production of H2 and a valuable protein from CO or syngas, providing envision to develop hyperthermophilic cell factory to upcycle industrial waste gas