Lignin-carbohydrate complex structures, their extraction, characterization, and impact on cellulase hydrolysis: A...

Lignocellulose, as a renewable feedstock, contains cellulose that can be hydrolyzed by cellulases into fermentable sugars for biofuel and chemical production. However, lignin-carbohydrate complex (LCC) significantly inhibits enzymatic hydrolysis efficiency by impeding enzyme accessibility to substrates. This review systematically summarizes the structural characteristics of LCC derived from non-wood, hardwood, and softwood sources, while evaluating the applicability and challenges of extraction and characterization techniques. It focuses on analyzing key parameters of LCC, including carbohydrate types, lignin unit ratios, linkage types (such as ester bonds, ether bonds, and phenyl glycoside bonds), and molecular weight to elucidate their regulatory mechanisms on productive/non-productive enzyme adsorption and substrate accessibility. These insights ultimately reveal LCCs' promoting or inhibitory effects on enzymatic hydrolysis. Unlike previous reviews that merely briefly mentioned the inhibitory effects of LCC on enzymatic hydrolysis or focused solely on LCC extraction and applications, this paper specifically examines both the promoting and inhibitory effects of LCC structures on enzymatic hydrolysis. It aims to provide guidance for developing pretreatment strategies that directionally regulate LCC structures, thereby achieving precise enhancement of lignocellulosic enzymatic hydrolysis efficiency.