l-lactic acid production using the syrup obtained in biorefinery of carrot discards

•Hugh quantities of carrot are discarded every year causing an environmental problem.•High levels of sugar remain in carrot syrup after fiber and beta-carotene extraction.•The use of carrot syrup is suitable to produce lactic acid at a low cost.•Fermentations resulted in 22.18g/L of l-lactic acid and a yield of 79.21%. The accumulation in large quantities of waste or by-products of diverse agricultural and industrial practices results not only in a deterioration of the environment but also in a loss of materials which can be processed to generate value-added products. A big amount of carrot discards is produced in the word by packing companies every year, because they do not meet the quality standards and the requirements of size and shape imposed by the consumer market. After extraction of beta-carotene from carrot discards, two by-products were obtained: dietary fibers and a syrup rich in fermentable sugars. The aim of this work was to evaluate the feasibility of using syrup of carrot discards as raw material to produce lactic acid employing two strains of Rhizopus spp. The maximum concentration of lactic acid (22.18g/L) was achieved using the strain of Rhizopus arrhizus (106conidia/mL) and carrot syrup supplemented with (NH4)2SO4, CaCO3 and other salts. Uniforms pellets were obtained by adding CaCO3 12h after the fermentation started.