A L-proline/O2 biofuel cell using L-proline dehydrogenase (LPDH) from Aeropyrum pernix

Microbial Proline Racemase-Proline Dehydrogenase Cascade for Efficient Production of D-proline and N-boc-5-hydroxy-L-proline from L-proline

D-proline and N-boc-5-hydroxy-L-proline are key chiral intermediates in the production of eletriptan and saxagliptin, respectively. An efficient proline racemase-proline dehydrogenase cascade was developed for the enantioselective production of D-proline. It included the racemization of L-proline to DL-proline and the enantioselective dehydrogenation of L-proline in DL-proline. The racemization of L-proline to DL-proline used an engineered proline racemase (ProR). L-proline up to 1000 g/L could be racemized to DL-proline with 1 g/L of wet Escherichia coli cells expressing ProR within 48 h. The efficient dehydrogenation of L-proline in DL-proline was achieved using whole cells of proline dehydrogenase-producing Pseudomonas pseudoalcaligenes XW-40. Moreover, using a cell-recycling strategy, D-proline was obtained in 45.7% yield with an enantiomeric excess of 99.6%. N-boc-5-hydroxy-L-proline was also synthesized from L-glutamate semialdehyde, a dehydrogenated product of L-proline, in a 16.7% yield. The developed proline racemase-proline dehydrogenase cascade exhibits great potential and economic competitiveness for manufacturing D-proline and N-boc-5-hydroxy-L-proline from L-proline.

Construction of a novel bioanode for amino acid powered fuel cells through an artificial enzyme cascade pathway

OBJECTIVE

The construction of a novel bioanode based on L-proline oxidation using a cascade reaction pathway comprised of thermostable dehydrogenases.

RESULTS

A novel multi-enzymatic cascade pathway, containing four kinds of dehydrogenases from thermophiles (dye-linked L-proline dehydrogenase, nicotinamide adenine dinucleotide (NAD)-dependent Δ¹-pyrroline-5-carboxylate dehydrogenase, NAD-dependent L-glutamate dehydrogenase and dye-linked NADH dehydrogenase), was designed for the generation of six-electrons from one molecule of L-proline. The current density of the four-dehydrogenase-immobilized electrode, with a voltage of + 450 mV (relative to that of Ag/AgCl), was 226.8 μA/cm² in the presence of 10 mM L-proline and 0.5 mM ferrocene carboxylate at 50 °C. This value was 4.2-fold higher than that of a similar electrode containing a single dehydrogenase. In addition, about 54% of the initial current in the multi-enzyme cascade bioanode was maintained even after 15 days.

CONCLUSIONS

Efficient deep oxidation of L-proline by multiple-enzyme cascade reactions was achieved in our designed electrode. The multi-enzyme cascade bioanode, which was built using thermophilic dehydrogenases, showed high durability at room temperature. The long-term stability of the bioanode indicates that it shows great potential for applications as a long-lived enzymatic fuel cell.