Production of poly (lactic acid) (PLA) from sisal waste

This study aimed at producing polylactic acid (PLA) from sisal waste because of its abundance and the need to address sisal waste management as well as limited products from the sisal plant that lead to low income in sisal industry. Environmental problems resulting from petrochemical based plastics (non-biodegradability, depletion, and increased consumption) and need for alternative raw material for Lactic acid (LA) production were also the basis for this study. There have so far been few or no studies on sisal boles to produce LA or PLA. A full factorial design was used to design the experiments and to evaluate the effects of temperature (60-100ºC), pH (1-5) and time (30-60 minutes) on sugar yield during hydrolysis; effects of initial sugar concentration (120-160 g/L), temperature (37-43ºC) and pH (5-6) on LA concentration, yield and productivity; effects of temperature (43-47ºC) and time (15-25 minutes) on LA concentration using modified hybrid short path evaporation system (M-HSPE) and effects of temperature (160-180ºC), time (1-2 hrs) and tin octoate catalyst concentration (0.025-0.05%) on the PLA yield during polymerization. Lactobacillus delbrueckii sp. delbrueckii was used in the fermentation process to produce LA. Developed juice extraction method produced 791±0.6 ml of juice per kg of sisal bole. Maximum production of LA was 24.2 ±0.02 g/L and a yield of 93%, which occurred at a temperature of 37ºC, initial pH of 6 and initial concentration of 120 g/L. It was possible to produce 0.73±0.05 g of lactide per g of sisal bole LA used. Almost 99% conversion of lactide into PLA was done for 2 hrs when the system temperature was 180ºC regardless of the catalyst ratio used. The current findings support sisal boles juice as an alternative feedstock for LA production, a precursor for PLA. This will protect environment by using waste and it is an opportunity to participate in a global move to ban the use of petrochemical plastics in packaging.