On-site glucohydrolase manufacture for 2nd generation integrated to 1st generation sugarcane bioethanol production

Sugarcane 2^nd generation bioethanol production integrated to a 1^st generation plant is regarded as a realistic arrangement to produce this biofuel in a cost effective way. However glucohydrolases (GHs) cost production has a prominent impact on bioethanol contribution cost. The maximization of bioreactor enzyme productivity and the use of low-cost carbon source are key factors to decrease the GH contribution cost to acceptable values. In order to decrease GH cost we have studied the on-site manufacture cellulosic enzyme production with Penicillium echinulatum and Trichoderma harzianum partially catabolite de-repressed strains. We proposed the use of pretreated sugarcane bagasse and sugarcane carbohydrate (sugar juice, molasses and sucrose) as cheap culture media components allied to fed-batch submerged controlled bioreactor cultivation as main strategies to achieve this goal. It was demonstrated that steam-exploded and hydrothermal pretreated sugarcane bagasse supplemented with sucrose and soybean flour in optimized ratios lead to enzyme broth activity up to 5 FPU/mL in approximately 144h of cultivation time (enzyme productivity of 35 FPU/L h) (Scenario 1). On the other hand the use of a controlled bioreactor fed-batch culture media profile precluded an enzyme productivity up to 70 FPU/L h (Scenario 2). Preliminary economic analysis indicated a GH contribution cost of US$ 0.11 / L of produced bioethanol for the Scenario 1 and US$ 0.07 / L of produced bioethanol for the Scenario 2. Enzyme cocktail produced in optimized conditions performed bagasse enzymatic hydrolysis comparable with commercial available cocktail.