Saccharification and Co-Fermentation of Ammoniated Corn Stover by Phaffia Rhodozyma for Astaxanthin Production

Abstract

High value co-products generated from waste agricultural feedstocks are important components that can improve economic conditions for integrated biorefineries. Red pigmented carotenoids, such as astaxanthin, are one type of co-product that can add value to biorefineries based on its wide range of uses that include supplementing aquaculture feed, natural dyes for fabrics, food, and pharmaceuticals. In this work, corn stover was ammoniated using the low moisture anhydrous ammonia (LMAA) process. The pretreated corn stover was then deconstructed and converted to astaxanthin using simultaneous saccharification and co-fermentation (SSCF) with the yeast strain Phaffia rhodozyma. Four different commercially available cellulase enzyme formulations were used to release monomeric sugars during SSCF. Two different enzyme formulations used for SSCF processing allowed for 4 mg/L astaxanthin to be produced. One interesting finding was that total sugar consumption did not correlate to higher astaxanthin titers. This result provides more evidence that astaxanthin generation from yeasts is tightly controlled based upon the availability of both carbon and nitrogen in the fermentation media.