Catalytic Performance of Food Additives Alum FlocculatingAgent Al(SO4)3 AlCl3 and OtherLewis Acids in Microwave Solvolysis of Hardwoods and RecalcitrantSoftwood for Biorefinery

摘要

The development of a novel pretreatment system using catalysts with high safety and low cost is pivotal to establish lignocellulosic biorefinery. We evaluated 16 Lewis acid catalysts for microwave solvolysis pretreatment to enhance enzymatic saccharification of woody biomass and found that very cheap and safe food additives, alum, are effective for the pretreatment, giving high sugar yield comparable to that of AlCl3, a strong Lewis acid catalyst effective both for softwood and hardwood. In microwave solvolysis of Japanese cedar, Paraserianthes falcataria and Eucalyptus globulus using alum in ethylene glycol/water (9/1, w/w), the maximum sugar yields after enzymatic saccharification reached 47.8, 51.0, and 59.7% based on the weight of each wood. The same reactions in glycol/water (9/1, w/w) gave the sugar yield, 34.5, 54.1, and 58.5%, indicating differential reactivity of the Lewis acid/solvent system depending on wood species. We found that efficiency and selectivity of pretreatment with a flocculating and astringent agent, Al2(SO4)3, was promoted by microwave. Reaction of Japanese beech wood with Al2(SO4)3 in 50% aqueous 1-propanol by microwave and conventional heatingrevealed that microwave irradiation suppressed excessive degradationof carbohydrates into furfural derivatives. Saccharification of thewood pretreated by microwave with 8 and 1 filter paper units of cellulolyticenzymes gave sugar yields per wood of 50.3 and 43.9%, whereas thesame reaction in an autoclave resulted in 48.9 and 34.7% yields, demonstratingthat microwave irradiation accelerated the saccharification and theeffect was remarkable with a lower enzyme dosage.