Fast and efficient alkaline peroxide treatment to enhance the enzymatic digestibility of steam‐exploded softwood substrates

Abstract

The enzymatic digestibility of steam‐exploded Douglas‐fir wood chips (steam exploded at 195°C, 4.5 min, and 4.5% (w/w) SO 2) was significantly improved using an optimized alkaline peroxide treatment. Best hydrolysis yields were attained when the steam‐exploded material was post‐treated with 1% hydrogen peroxide at pH 11.5 and 80°C for 45 min. This alkaline peroxide treatment was applied directly to the water‐washed, steam‐exploded material eliminating the need for independent alkali treatment with 0.4% NaOH, which has been traditionally used to post‐treat wood samples to try to remove residual lignin. Approximately 90% of the lignin in the original wood was solubilized by this novel procedure, leaving a cellulose‐rich residue that was completely hydrolyzed within 48 h, using an enzyme loading of 10 FPU/g cellulose. About 82% of the originally available polysaccharide components of the wood could be recovered. The 18% of the carbohydrate that was not recovered was lost primarily to sugar degradation during steam explosion. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 678–684, 2002; DOI 10.1002/bit.10159