The objective of this study was to explore the fungal bioconversion of left –over biomass hydrolysates into priority chemicals using lab scale experiments, and forming a purified Itaconic acid solid product for the first time. The use of rice husks for this sustainable production was studied under multivariate conditions. With the use of 3.4% (v v-1) H3PO4, 145 °C (48 bar) and 28 min hydrolysis time, 44.4 g sugar L-1 was produced (yield of 266.4 mg sugar g-1 rice husks). Using 3.8% (v v-1) HNO3, the best hydrolysis condition was 135 °C (45 bar) and 35 min reaction time, when 42.0 g sugar L-1 was produced (yield of 252.0 mg sugar g-1 rice husks). This is higher than the corresponding results of those obtained in the literature. The fermentation was conducted under optimized multivariate conditions, at 30 ºC, using phosphoric hydrolysate and an addition of 10 g L-1 yeast extract, pH 6.0 adjusted with CaO(s) and the use of Aspergillus terreus (ATCC 10020). Besides using no carbon supplementation, the optimized experiment produced 1.9 g itaconic acid L-1 (yield of 49 mg g-1 sugar), similar results to that obtained with supplementation found in the literature for other kinds of lignocellulosic materials.