Optimization of Culture Conditions for Growth Associated with Cr(VI) Removal by Wickerhamomyces anomalus M10

Chromate-resistant microorganisms with the ability of reducing toxic Cr(VI) to less toxic Cr(III), are candidates for bioremediation. An alternative culture medium to reduce Cr(VI) using Wickerhamomyces anomalus M10 was optimized. Using the Plackett-Burman design, it was determined that sucrose, K2HPO4 and inoculum size had significant effects on chromate removal (i.e., reduction) at 24 h. Concentrations of these significant factors were adjusted using a complete factorial design. In this case, only the K2HPO4 effect was significant at 12 h of culture, with greater Cr(VI) removal at low concentration (1.2 g L-1). The optimum medium was validated at the fermenter scale level. Optimal culture conditions for complete removal of Cr(VI) (1 mM) were 400 rpm agitation and air flow of 1 vvm. Moreover, W. anomalus M10 completely removed consecutively added pulses of Cr(VI) (1 mM). These results show interesting characteristics from the standpoint of biotechnology because the development of a future remediation process using W. anomalus M10 can represent an efficient and highly profitable technology for removing the toxic form of Cr.