Probing the nature of AFEX-pretreated corn stover derived decomposition products that inhibit cellulase activity

James F. Humpula, Nirmal Uppugundla, Ramin Vismeh, Leonardo Sousa, Shishir P. S. Chundawat, A. Daniel Jones, Venkatesh Balan, Bruce E. Dale, Albert M. Cheh
Sequential fractionation of AFEX-pretreated corn stover extracts was carried out using ultra-centrifugation, ultra-filtration, and solid phase extraction to isolate various classes of pretreatment products to evaluate their inhibitory effect on cellulases. Ultra-centrifugation removed dark brown precipitates that caused no appreciable enzyme inhibition. Ultra-filtration of ultra-centrifuged AFEX-pretreated corn stover extractives using a 10 kDa molecular weight cutoff (MWCO) membrane removed
more » ... itional high molecular weight components that accounted for 24–28% of the total observed enzyme inhibition while a 3 kDa MWCO membrane removed 60–65%, suggesting significant inhibition is caused by oligomeric materials. Solid phase extraction (SPE) of AFEX-pretreated corn stover extractives after ultra-centrifugation removed 34–43% of the inhibition; ultra-filtration with a 5 kDa membrane removed 44–56% of the inhibition and when this ultra-filtrate was subjected to SPE a total of 69–70% of the inhibition were removed. Mass spectrometry found several phenolic compounds among the hydrophobic inhibition removed by SPE adsorption.
doi:10.7282/t3t43wcr fatcat:6uyxwrykqjdzljsgxhu3mkfhcy