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Effective delignification and decrystallization of cauliflower wastes by using dilute phosphoric acid for efficient enzymatic digestibility to produce fermentable sugars

Majumdar, Sayari, Naha, Antara, Bhattacharyya, D.K., Bhowal, Jayati
Biomass and bioenergy 2019 v.125 pp. 169-179
X-ray diffraction, biomass, cauliflower, cellulose, cellulosic fibers, crystal structure, delignification, endo-1,4-beta-glucanase, enzymatic hydrolysis, feedstocks, hemicellulose, leaves, lignin, pH, phosphoric acid, porosity, reducing sugars, saccharification, scanning electron microscopy, temperature, wastes
The present study investigated the feasibility of using cauliflower wastes (stalk and leaf) as novel feedstock for production of fermentable sugars, thus reducing the wastage. In this investigation cauliflower wastes were pretreated with dilute phosphoric acid (H3PO4) prior to enzymatic hydrolysis for better release of fermentable sugars. Maximum total reducing sugar yields were achieved at 121 °C, 4% v/v dilute H3PO4 concentration and 60 min for both the waste biomasses. The structural analysis of raw and pretreated cauliflower wastes was investigated. The surface morphological changes of cauliflower waste biomasses revealed that removal of hemicellulose and lignin during dilute H3PO4 pretreatment exposed cellulose fibers resulting in the destruction of the recalcitrant structure of biomasses. SEM and XRD analysis revealed that the crystalline structure of cellulose in the pretreated biomasses was transformed from cellulose I to the amorphous form causing changes in the porosity and cellulose crystallinity index. The pretreatment process have demonstrated improved yield of cellulose by removal of physical barriers namely, hemicellulose and lignin from the waste biomasses. The cellulose conversion to fermentable sugar was significantly greater for pretreated biomasses. After enzymatic saccharification with commercial cellulase, Celluclast® at the same pretreatment conditions cellulose conversion to fermentable sugar were found to be significantly increased than those of untreated biomasses. The optimum operation condition of enzymatic hydrolysis of 4% v/v dilute H3PO4 pretreated cauliflower wastes were biomass loading of 1.2% w/v, enzyme loading 15 U/g, pH 4, incubation temperature 50 °C and incubation time 180 min.