Method for preparing sugar, bioethanol or microbial metabolite from lignocellulosic biomass

A method of producing fermentable sugar, the method comprising the steps of:

• performing liquid hot water pretreatment of a lignocellulosic biomass at 160 to 230° C. temperature to produce a pretreatment product;
• treating said pretreatment product with an aqueous alkali solution at pH 11 or higher and 80 to 105° C. temperature;
• adjusting pH to 5.0+0.1 by adding a base having at least two hydroxyl groups, wherein the base is present in a form of an aqueous solution or a colloidal suspension having an average diameter of 0.001 to 10 μm, wherein the base forms a salt by neutralization reaction with acetic add produced by hydrolysis of the pretreatment product, and a dissolution constant (pKa2) of a second acetyl group of the resulting salt is 8.0 or more;
• contacting the pretreatment product after said adjusting with a cellulose hydrolyzing enzyme, and producing fermentable sugar solution having at least 9±1% acetic add by weight, relative to total sum of glucose, other sugars, acetic acid, 5-hydroxymethyl-2-furaldehyde (HMF), and furfural in the fermentable sugar solution.