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Dilute-sulfuric acid pretreatment of de-starched cassava stems for enhancing the enzymatic convertibility and total glucan recovery

Martín, Carlos, Peinemann, Jan Christoph, Wei, Maogui, Stagge, Stefan, Xiong, Shaojun, Jönsson, Leif J.
Industrial crops and products 2019 v.132 pp. 301-310
amylases, byproducts, cassava, cellulose, digestion, enzymatic hydrolysis, experimental design, feedstocks, fuels, starch, stems, sulfuric acid, temperature
Cassava stems are an abundant feedstock that is becoming attractive for biochemical conversion to fuels and chemicals. Since cassava stems are rich in both cellulose and starch, carefully designed pretreatment and digestion procedures are required for achieving high glucan recovery. In this study, partially de-starched cassava stems resulting from a water extraction stage were hydrolyzed with amylases, and the resulting starch-depleted material was pretreated with dilute sulfuric acid, and submitted to enzymatic hydrolysis of cellulose. The effects of acid pretreatment on glucan recovery, enzymatic convertibility, and by-product formation were investigated using a Box-Behnken experimental design with temperature (165–195 °C), time (5–35 min), and acid concentration (0.2–1.0%) as independent variables. In further experimental series, the time period was extended up to 110 min while maintaining temperature at 195 °C and sulfuric acid concentration at 0.6%. Using those conditions, pretreatment for 50 min gave the best results (83.8% enzymatic convertibility of pretreated cellulose, and ˜72% overall glucan-to-glucose conversion).