Production of 3‐hydroxypropionic acid from glycerol by recombinant Klebsiella pneumoniae Δ dhaT Δ yqhD which can produce vitamin B 12 naturally

• Published in: Biotechnology and bioengineering 2013-02, Vol.110 (2), p.511-524
• Main Authors: Ashok, Somasundar, Sankaranarayanan, Mugesh, Ko, Yeounjoo, Jae, Kyeung‐Eun, Ainala, Satish Kumar, Kumar, Vinod, Park, Sunghoon
• Format: Article
• Language: English
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.24726

3‐Hydroxypropionic acid (3‐HP) is an important platform chemical that can be used to synthesize a range of chemical compounds. A previous study demonstrated that recombinant Escherichia coli stains can produce 3‐HP from glycerol in the presence of vitamin B 12 (coenzyme B 12 ), when overexpressed with a coenzyme B 12 ‐dependent glycerol dehydratase (DhaB) and an aldehyde dehydrogenase. The present study examined the production of 3‐HP in recombinant Klebsiella pneumoniae strains, which naturally synthesizes vitamin B 12 and does not require supplementation of the expensive vitamin. The NAD + ‐dependent gamma‐glutamyl‐gamma‐aminobutyraldehyde dehydrogenase (PuuC) of K. pneumoniae alone or with its DhaB was overexpressed homologously, and two major oxidoreductases, DhaT and YqhD, were disrupted. Without vitamin B 12 addition, the recombinant K. pneumoniae Δ dhaT Δ yqhD overexpressing PuuC could produce ∼3.8 g/L 3‐HP in 12 h of flask culture. However, this was possible only under the appropriate aeration conditions; 1,3‐propanediol (1,3‐PDO) (instead of 3‐HP) was mainly produced when aeration was insufficient, whereas a very small amount of both 3‐HP and 1,3‐PDO were produced when aeration was too high. The production of a small amount of 3‐HP under improper aeration conditions was attributed to either slow NAD + regeneration (under low aeration) or reduced vitamin B 12 synthesis (under high aeration). In a glycerol fed‐batch bioreactor experiment under a constant DO of 5%, the strain, K. pneumoniae Δ dhaT Δ yqhD , overexpressing both PuuC and DhaB could produce >28 g/L 3‐HP in 48 h with a yield of >40% on glycerol. Only small amount of 3‐HP was produced when cultivation was carried out at a constant aeration of 1 vvm or constant 10% DO. These results show that K. pneumoniae is potentially useful for the production of 3‐HP in an economical culture medium that does not require vitamin B 12 . The results also suggest that the aeration conditions should be optimized carefully for the efficient production of 3‐HP while using this strain. Biotechnol. Bioeng. 2013; 110: 511–524. © 2012 Wiley Periodicals, Inc.