Integrated fermentative production and downstream processing of L-malic acid by Aspergillus wentii using cassava peel waste

L-malic acid (L-MA) is an industrially significant chemical with enormous potential. The fungal cell factories could be exploited to harvest it on large scales. In our study, Aspergillus wentii strain (MTCC 1901 T) was explored for L-MA production. Initially, the L-MA production was carried out using glucose with optimization of parameters influencing product accumulation (pH and CaCO3). The fermentation resulted in L-MA titer of 37.9 g/L with 0.39 g/g yield. Then, cassava peel waste (CPW) was used for L-MA production by separate hydrolysis and fermentation. Optimized acidic and enzymatic hydrolysis resulted in glucose release of 0.53 and 0.66 g/g CPW, respectively. The strain accumulated 20.9 g/L and 33.1 g/L L-MA with corresponding yields of 0.25 g/g and 0.34 g/g during batch cultivation using acid and enzyme hydrolysate, respectively. Finally, the produced L-MA was separated using an inexpensive solvent extraction method. Among various solvents used, n-butanol exhibited maximum L-MA extraction efficiency (31%).