METHODS AND RESULTS:
In this study, genetically engineered Pseudomonas putida TODE1 served as a biocatalyst for the bioproduction of valuable 3-methylcatechol (3MC) from toluene in an aqueous-organic two-phase system. The two-phase system was used as an approach to increase the biocatalyst efficiency.Among the organic solvent tested, n-decanol offered several benefits including having the highest partitioning of 3MC, with a high 3MC yield and low cell toxicity. The effect of media supplementation with carbon/energy sources (glucose, glycerol, acetate and succinate), divalent metal cations (Mg(2+), Ca(2+), Mn(2+) and Fe(2+)), and short-chain alcohols (ethanol, n-propanol and n-butanol) as a cofactor regeneration system on the toluene dioxygenase (TDO) activity, cell viability, and overall 3MC yield were evaluated. Along with the two-step cell preparation protocol, supplementation of the medium with 4 mM glycerol as a carbon/energy source, and 0.4 mM Fe(2+) as a cofactor for TDO significantly enhanced the 3MC production level.
When in combination with the use of n-decanol and n-butanol as the organic phase, a maximum overall 3MC concentration of 31.8 mM (166 mM in the organic phase) was obtained in a small-scale production, while it was at 160.5 mM (333.2 mM in the organic phase) in a 2-L scale.
CONCLUSIONS:
To our knowledge, this is the highest 3MC yield obtained from a TDO-based system so far. |
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