Citrobacter werkmanii, a new candidate for the production of 1,3-propanediol: strain selection and carbon source optimization

In the past decade 1,3-propanediol (PDO) has been identified as one of the top added value bio-based chemical building blocks in many reports, leading to Klebsiella sp., Clostridium sp., and Escherichia coli based production platforms. However, Citrobacter sp. are also known to naturally produce PDO. In this work a range of Citrobacter sp. has been screened for their PDO production capacity and their natural resistance against high PDO titers, leading to the selection of a new candidate for the production of PDO from glycerol, namely Citrobacter werkmanii DSM17579. In batch fermentation, a production rate of 2.84 g L-1 h(-1) and a yield of 0.62 mol mol(-1) glycerol were obtained starting from 60 g L-1 and 20 g L-1 of glycerol, respectively. The metabolism of this organism was further studied by perturbing it with 18 carbon sources as co-substrates. These results pointed to the potential use of cheap waste streams such as ligno/hemicellulosic hydrolysates for the production of PDO. Furthermore, the sugar alcohol D-mannitol and D-galactose enhance the production yield significantly (0.83 mol mol(-1) and 0.81 mol mol(-1), respectively, an enhancement of about 30% compared to glycerol as the sole carbon source). The latter indicates the potential of whey based waste streams for the production of PDO. These are, to date, the highest yields reported for natural producing Enterobacteriaceae using co-substrates for the production of PDO from glycerol.