Possible ways of bio-refining and utilizing the residual lignocelluloses of corn growing and processing

Abstract

The events of the past five years showed that the most promising alternative liquid fuel is the bioethanol, which could replace fossil fuels, thus impeding the further acceleration of the global warming. The bioethanol production of the world showed a significant growth, which was basically caused by the increase of corn starch processing and fermentation. However, the growing and the processing of corn results in lignocellulosic by-products like corn stover, corncob, corn fiber, and press cake. The weight of the starch is only ∼25% of the whole corn plant. The further increase of corn growing and processing will increase the production of the lignocellulosic by-products as well.The idea of "bio-refining" means the fractionation of the biomass with chemical and biotechnological methods, and producing value added products from each fraction. The goal of most researches in the field of lignocellulose utilization is the production of ethanol. Most authors conclude that it is not economical because of the high ratio of the yet unutilizable fractions, like hemicellulose and lignin. But if these fractions could be sharply separated, and converted to valuable products, the whole process of lignocellulose utilization (bio-refining) could be economically feasible. The scope of this study was to review and evaluate all of the presently available methods for separating the fractions of lignocellulosic biomasses, and for utilizing them. Over one hundred publications were reviewed from the fields of biotechnology, food chemistry, and chemical technology to collect all processes for lignocellulose utilization.

Investigation of selective arabinose release from corn fibre by acid hydrolysis under mild conditions

“…Corn fibre hemicelluolse is considered one of the most complex heteropolysaccharids recalcitrant to enzymatic hydrolysis . However, it can be easily solubilized at relatively mild conditions by mineral acids …”

“…19 However, it can be easily solubilized at relatively mild conditions by mineral acids. 1,2,11,20 Corn fibre is utilized mainly as low-value animal feed, or solid fuel in pelletized form, however, it is a promising raw material for producing value-added products. 21 -23 The main fields of research concerning corn fibre utilization are the production of bioethanol 6,24 and food additives like cellulosic fibre gel, 25 corn fibre gum, 26 xylo-oligosaccharide prebiotics, 27 corn fibre oil, 28 ferulic acid, 29 xylitol 30 -32 and vanillin.…”

Investigation of commercial enzyme preparations for selective release of arabinose from corn fibre

“…Corn fibre, a low‐value by‐product of the corn wet milling process, is an appropriate raw material for producing sugars including L‐arabinose . Corn fibre has been used as a low‐grade animal feed ingredient or as solid fuel in pelletized form, however it can also be converted into value‐added products in a biorefinery concept . Corn fibre dry matter contains about 20% starch, 14% cellulose and 35% hemicellulose .…”

Processing sweet sorghum into bioethanol – an integrated approach

“…Contrarily to first generation ethanol production that uses starch or sucrose containing feedstock, second generation ethanol production is based on lignocellulosic biomass [11]. However, because of the more resistant structure of lignocellulosic materials, the enzymatic hydrolysis must be preceded by pretreatment that aims to set cellulose chains free of the lignin matrix to be available for enzymes and eliminate the other component of lignocelluloses, namely the hemicelluloses (composed mostly of pentoses) in a soluble form [2].…”