Production of reducing sugar in Gracilaria verrucosa using physio-chemical pretreatment and subsequent enzymatic hydrolysis

In this work, the production of reducing sugar from Gracilaria verrucosa using physiochemical pretreatment (ultrasonication with acid catalyst) and subsequent enzymatic hydrolysis was investigated. The pretreatment yield was 60.38% when 2% (w/v) G. verrucosa was treated with 100 mM of sulfuric acid and 60% ultrasonic amplitude at unregulated temperature for 60 min. Additionally, subsequent enzymatic hydrolysis increased the yield of reducing sugar to 76.26%. Furthermore, physiochemical pretreatment significantly reduced the formation of 5-hydroxymethylfurfural (a fermentation inhibiting compound) and the time required for completing enzymatic hydrolysis compared to hydrothermal pretreatment. Finally, the physiochemical pretreatment method, which includes ultrasonication and an acid catalyst, is feasible and has the potential to convert macroalgae to sugars.