Improvement of methyl ester and itaconic acid production utilizing biorefinery approach on Scenedesmus sp.

Abstract

This study aims to utilize the Scenedesmus sp. to produce methyl ester and itaconic acid as a biorefinery approach. The wet biomass was utilized for direct transesterification using potassium carbonate as catalyst. The reaction parameters such as solvent to algae ratio, water addition, catalyst concentration, temperature, and reaction time parameters were optimized. Under optimized conditions (20 ml/g solvent to algae ratio, 40% water addition, 4% catalyst, 60 °C and 60 min), a yield of 93% methyl ester yield was achieved. The obtained methyl ester showed satisfactory fuel properties. The spent biomass after transesterification was further subjected to hydrolysis using H2SO4 combined with ultrasound. The sugar content in the hydrolysate accounted for 92% sugar recovery which was further used for the itaconic acid production using Aspergillus sp. The itaconic acid production was improved by altering the MgSO4 concentration in the medium. Addition of TCA cycle metabolites further enhanced the itaconic acid production. Under optimized conditions (50 g/l sugar, 5 ml inoculum, 0.4 g/l MgSO4, 4 mM citric acid, 37 °C for 7 days with 120 rpm), a maximum itaconic production yield of 0.0692 g/g of Scenedesmus sp. was achieved when 4 mM citric acid was added to the medium which suggested an important role of TCA cycle to supply intermediates for the synthesis of itaconic acid.