Fig. 4From: Comparative study of acid- and alkali-catalyzed 1,4-butanediol pretreatment for co-production of fermentable sugars and value-added lignin compoundsSEM observations of the raw and pretreated biomass: raw biomass (a); HCl-BDO pretreated solid at 10Â mM (b) and 40Â mM (c); NaOH-BDO pretreated solid at 250Â mM (d) and 400Â mM (e)Back to article page