Redox Balanced Co-production of Propanediol and 3-Hydroxypropionic Acid from Glycerol Using Novel Recombinant Klebsiella quasipneumonia MSN12

The redox imbalance is the major obstacle in the microbial production of 3-hydroxypropionic acid (3-HP). Co-production of propanediol (PDO) and 3-HP is an effective strategy to overcome the redox imbalance issue. The biocatalyst Klebsiella pneumoniae naturally co-produces PDO and 3-HP. Its poor growth characteristics and excessive production of lipopolysaccharide hurdle its usage in industries. The objective of this study is to circumvent these constraints by isolating a novel strain of K. quasipneumoniae MSN12 ( Kp MSN12) from soil samples. From a numerous isolate, the new isolate Kp MSN12 has produced 58 mM PDO and 4 mM 3-HP, when it was grown in shake flask under microaerobic conditions, which is higher than the control Kp 109. The effect of overexpression of an aldH ( KGSADH ) on co-production of 3-HP and PDO from glycerol was investigated in recombinant Kp MSN12 ( Kp MSN12K). Kp MSN12K produced 45 mM of 3-HP and 30 mM PDO which was observed higher (3-HP 25 mM, PDO 28 mM) than the control strain. While over expressing dhaB in another recombinant ( Kp MSN12D), 3-HP was reduced to 9 mM and 11 mM PDO due to the accumulation of 3-HPA and the growth was severely hampered. In addition, combined overexpression of dhaB and aldH ( Kp MSN12DK) produced 33 mM 3-HP and 25 mM PDO. The lower lipopolysaccharide content in the Kp MSN12 strain was confirmed by comparing 2-keto3-deoxyoctonate content ( Kp MSN12—3.8 µg/mL; Kp 109—5.14 µg/mL). In addition, this new strain exhibited enhanced sedimentation characteristics and higher susceptibility to a variety of antibiotics when compared to Kp 109 strain. These potential characteristics of Kp MSN12 would shape it as a desirable host for the production of industrial chemicals. Graphical Abstract