Abstract
Kraft pulp enzymatic hydrolysis is a promising method of woody biomass bioconversion. The influence of composition and structure of kraft fibers on their hydrolysis efficiency was evaluated while using four substrates, unbleached hardwood pulp (UHP), unbleached softwood pulp (USP), bleached hardwood pulp (BHP), and bleached softwood pulp (BSP). Hydrolysis was carried out with Penicillium verruculosum enzyme complex at a dosage of 10 filter paper units (FPU)/g pulp. The changes in fiber morphology and structure were visualized while using optical and electron microscopy. Fiber cutting and swelling and quick xylan destruction were the main processes at the beginning of hydrolysis. The negative effect of lignin content was more pronounced for USP. Drying decreased the sugar yield of dissolved hydrolysis products for all kraft pulps. Fiber morphology, different xylan and mannan content, and hemicelluloses localization in kraft fibers deeply affected the hydrolyzability of bleached pulps. The introduction of additional xylobiase, mannanase, and cellobiohydrolase activities to enzyme mixture will further improve the hydrolysis of bleached pulps. A high efficiency of never-dried bleached pulp bioconversion was shown. At 10% substrate concentration, hydrolysates with more than 50 g/L sugar concentration were obtained. The bioconversion of never-dried BHP and BSP could be integrated into working kraft pulp mills.
Highlights
Lignocelluloses have been the focus of much attention as promising feedstock for the sustainable production of non-food-derived sugars, from the viewpoint of both energy and the environment.Numerous physical, chemical, and biological methods for converting lignocellulose to sugars are underCatalysts 2020, 10, 536; doi:10.3390/catal10050536 www.mdpi.com/journal/catalystsCatalysts 2020, 10, 536 development, but those that rely on enzymes are attractive
The present study examined the biocatalysis of four substrates (UHP, unbleached softwood pulp (USP), bleached hardwood pulp (BHP), and bleached softwood pulp (BSP)) by the Penicillium verruculosum enzyme complex
The assumed conditions of enzymatic hydrolysis at a substrate concentration of 5–10% with a Penicillium verruculosum enzyme complex dosage of 10 filter paper units (FPU)/g of pulp can be acceptable for obtaining hexoses and pentoses in industry
Summary
Lignocelluloses have been the focus of much attention as promising feedstock for the sustainable production of non-food-derived sugars, from the viewpoint of both energy and the environment.Numerous physical, chemical, and biological methods for converting lignocellulose to sugars are underCatalysts 2020, 10, 536; doi:10.3390/catal10050536 www.mdpi.com/journal/catalystsCatalysts 2020, 10, 536 development, but those that rely on enzymes are attractive. Lignocelluloses have been the focus of much attention as promising feedstock for the sustainable production of non-food-derived sugars, from the viewpoint of both energy and the environment. Chemical, and biological methods for converting lignocellulose to sugars are under. Enzymes can potentially serve as industrial catalysts for biomass conversion, providing benefits, such as high specificity, low energy, and reagent consumption, and little environmental pollution [1]. The conversion of lignocellulosic biomass into simple carbohydrates, phenolics, aromatics, and other substances remains a major challenge. The resulting conversion of cellulose to glucose can produce a number of useful products, including biofuels, as well as different organic acids. Lignocellulose is a very challenging material for enzymatic attack, due to its complex and compact structure composed of many biopolymers, each with a different chemical composition and physical structure [2]
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