Toxicity of synthetic colorants used in foods, pharmaceuticals and cosmetic preparations led to increased research for natural pigments sources. Fungi provide a readily available alternative source of natural pigments. In the biotechnology industry, growing demands to increase production yields at lower costs require use of inexpensive and/or waste feedstock and a process improvement. Corncobs are lignocellulosic waste product representing up to 30 % of corn by weight. These materials represent an abundant and inexpensive source of sugars which can be biotechnologically converted to industrial products. The feasibility of corncob hydrolysate as an alternative substrate was investigated in this study.
Hydrolysis of the sugars oligomers to the correspondent monomers was performed using a dilute sulphuric acid hydrolysis. Two factors were studied, acid concentration (0.5, 1.0, 1.5 % v/v) and treatment time (30, 60, 90 min). The maximum xylose yield was obtained using 1.5 % H2SO4 v/v and at 90 min of treatment 35 gL-1. Hydrolysis treatments resulted in the release of some inhibitory compounds such as acetic acid and formic acid; and removal of these toxic compounds was attempted using activated charcoal. The obtained liquor was used for the submerged fermentation production of pigments. Different media composition were analyzed: a) Corncob liquor, b) Corncob liquor and Czapek salts, c) Diluted corncob liquor to adjust xylose concentration (15 gL-1), d) Diluted corncob liquor to adjust xylose concentration (15 gL-1) and Czapeck salts. Conventional xylose medium (Czapeck medium) was used as a control.
Results showed that the diluted corncob liquor medium (c) yields (OD500nm=8.0) were close to those obtained by the control (OD500nm=10.0). Corncob hydrolysate was proved to be an efficient alternative medium for pigment production by Penicillium purpurogenum; however cultivation conditions need to be optimized in order to enhance pigment production.