Bioconversion of Giant Cane for Integrated Production of Biohydrogen, Carboxylic Acids, and Polyhydroxyalkanoates (PHAs) in a Multistage Biorefinery Approach

A highly productive Arundo donax L. clone (Clone AD-20) was produced at full field to give 54.6 Mg total solids biomass Ha-1. Biomass was chemically and enzymatically pretreated, recovering 13.9 Mg Ha-1 of glucose and 3.6 Mg Ha-1 of xylose, i.e., 3.5-4.5 more than yield typically obtained from corn stover or switchgrass. The subsequent fermentation of the liberated sugars to organic acids (OA) by dark fermentation generated yields of 3850 Nm3 Ha-1 of biohydrogen and 14.2 Mg Ha-1 of OAs. OAs were then used as a feed to produce polyhydroxyalkanoates (PHA), with 3-hydroxybutyrate the major monomer present (PHB > 95% PHA), from a biological process using mixed microbial culture producing 5.04 Mg Ha-1 of PHA. An initial economic analysis indicated that this multistage biorefinery approach would result in a net revenue of 10,415 € Ha-1, which is approximately 9-fold greater than that obtained by a traditional biorefinery producing bioethanol.