Abstract
A continuous packed bed reactor for NADH-dependent biocatalysis using enzymes co-immobilized on a simple carbon support was optimized to 100% conversion in a residence time of 30 min. Conversion of pyruvate to lactate was achieved by co-immobilized lactate dehydrogenase and formate dehydrogenase, providing in situ cofactor recycling. Other metrics were also considered as optimization targets, such as low E factors between 2.5–11 and space-time yields of up to 22.9 g L–1 h–1. The long-term stability of the biocatalytic reactor was also demonstrated, with full conversion maintained over more than 30 h of continuous operation.
Highlights
The push toward greener, more efficient methods for chemical production is currently a major focus of the pharmaceutical and fine-chemical industries, driven by economic, environmental, and regulatory factors.[1−4] Biocatalysts are known for their excellent selectivity under mild reaction conditions and are widely seen as a greener alternative to traditional chemical synthesis methods,[5,6] for chiral products
Cofactor regeneration was provided by the NAD+-dependent conversion of formate to Scheme 1. (A) NADH-Dependent Biocatalytic Conversion of Pyruvate to Lactate; (B) Flow Reactor Setupa aLegend for flow reactor setup: (i) reaction solution vessel; (ii) syringe pump; (iii) packed bed reactor; (iv) fraction collector; LDH = lactate dehydrogenase; FDH = formate dehydrogenase; ● = enzymemodified carbon particle; ○ = glass bead
We have presented the use of a simple carbon support for straightforward co-immobilization of NADH-dependent LDH with FDH to facilitate ketone reduction with in situ cofactor recycling in a continuous packed bed reactor
Summary
The push toward greener, more efficient methods for chemical production is currently a major focus of the pharmaceutical and fine-chemical industries, driven by economic, environmental, and regulatory factors.[1−4] Biocatalysts are known for their excellent selectivity (removing the need for protection/ deprotection steps) under mild reaction conditions and are widely seen as a greener alternative to traditional chemical synthesis methods,[5,6] for chiral products. Immobilization of biocatalysts can lead to improved stability and increase enzyme lifetimes.[10−12] Recent advances in enzyme immobilization have exploited techniques such as HaloTag[13] and histidine tagging of proteins as well as the use of a range of support materials, including resins,[14] agarose,[15] and microbeads.[16] many of these enzyme immobilization techniques require expensive supports, modification of the support and/or enzyme, or lengthy immobilization times and can cause a significant loss of activity compared with the free enzyme in solution Flow chemistry is another powerful technique for greener, more efficient chemical production that has gained in importance in recent years.[17−19] Flow reactors can offer improved heat and mass transfer and a smaller footprint compared with batch reactors for the same product yield. The use of similar carbon supports could offer a route to implementing biocatalysis in industry-standard flow reactors
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