Development of a process for the direct production of 1,4-butanediol from cellulosic feedstocks

Genomatica has developed a commercial process for the direct production of 1,4-butanediol (BDO) from sugars. In order to increase the flexibility of the process and adapt it for use with even more economical feedstocks, Genomatica is developing a biomass sugar-to-BDO process. A major effort within this program is the development of BDO-producing Escherichia coli strains that can co-ferment C5 and C6 sugars. One approach that has been successfully employed is adaptive evolution to select for strain variants that can efficiently co-utilize glucose and xylose. The genome of one improved clone was sequenced and a candidate allele responsible for this phenotype was introduced into naïve BDO producing E. coli strains. Further analyses revealed that gene modifications essential for increasing BDO yield deleteriously affected sugar co-utilization rates. Use of 13-C metabolic flux analysis and metabolomics identified the primary constraints. Biomass sugars from different suppliers using processes varying from steam explosion and enzymatic saccharification to acid hydrolysis have been evaluated with respect to titer, rate, yield and recovery of BDO using the dextrose process as the benchmark. These studies have shed light on the requirements for engineering bacterial strains that are robust for use with multiple feedstocks in a commercially viable BDO process.