Evaluation of ozonolysis in acid and alkaline conditions as pretreatment of sugarcane bagasse

The zonolysis is an attractive alternative to biomass pretreatment because is an efficient form to oxidize highly recalcitrant compounds without use of high temperature and pressure or toxic compounds. We evaluated the yields of glucose recovery after enzymatic saccharification of sugarcane bagasse pretreated in different conditions of pH (acid H₂SO₄, or alkaline NaOH), solution concentration (0.5 or 0.1 M) and time reaction (30 or 60 minutes) during ozonolysis through a Full Factorial Design 2³ with 16 runs (8 treatments in duplicate). Pretreatments were performed using 25 grams dry substrate in a fixed bed column under saturated O₃ flux. The resulting samples were washed and dried before saccharification. The enzymatic hydrolysis was carried out in sodium citrate buffer 0.1 M, pH 4.8-5.2 with 10.0% (w/v) solids load, commercial enzymes (Cellic^® Ctec2:Htec2; 0,02 gram protein /gram bagasse), 150 r.p.m. and 50 °C for 24 hours. The glucose release was higher in alkaline treatment (0.1 M; 60 min) with 24.5 g L^-1 and 51.2% yield to cellulose into glucose. The yields for acid treatment (0.5M; 60 min) and the non-treated bagasse were significantly lower (0.5M; 60 min) (15.6 g L^-1; 32.7% yield and 9.6 g L^-1; 20.1% yield). The treatment using water produced 21.5 g L^-1glucose (45.1% yield). After washing, cellulose conversion to glucose increased in all samples, and the water+ozone pretreatment resulted in the highest yield (60%). These results demonstrate ozonolysis can be successfully performed in water followed by washing, or under alkaline media without washing.

ACKNOWLEGMENTS: CAPES, CNPq and FAPESP