Biosynthesis of 2-hydroxyisobutyric acid (2-HIBA) from renewable carbon

Abstract

Nowadays a growing demand for green chemicals and cleantech solutions is motivating the industry to strive for biobased building blocks. We have identified the tertiary carbon atom-containing 2-hydroxyisobutyric acid (2-HIBA) as an interesting building block for polymer synthesis. Starting from this carboxylic acid, practically all compounds possessing the isobutane structure are accessible by simple chemical conversions, e. g. the commodity methacrylic acid as well as isobutylene glycol and oxide. During recent years, biotechnological routes to 2-HIBA acid have been proposed and significant progress in elucidating the underlying biochemistry has been made. Besides biohydrolysis and biooxidation, now a bioisomerization reaction can be employed, converting the common metabolite 3-hydroxybutyric acid to 2-HIBA by a novel cobalamin-dependent CoA-carbonyl mutase. The latter reaction has recently been discovered in the course of elucidating the degradation pathway of the groundwater pollutant methyl tert-butyl ether (MTBE) in the new bacterial species Aquincola tertiaricarbonis. This discovery opens the ground for developing a completely biotechnological process for producing 2-HIBA. The mutase enzyme has to be active in a suitable biological system producing 3-hydroxybutyryl-CoA, which is the precursor of the well-known bacterial bioplastic polyhydroxybutyrate (PHB). This connection to the PHB metabolism is a great advantage as its underlying biochemistry and physiology is well understood and can easily be adopted towards producing 2-HIBA. This review highlights the potential of these discoveries for a large-scale 2-HIBA biosynthesis from renewable carbon, replacing conventional chemistry as synthesis route and petrochemicals as carbon source.

Novel Coenzyme B12-dependent Interconversion of Isovaleryl-CoA and Pivalyl-CoA

“…However, consumption of valeryl-CoA was not observed in the presence of IcmF, AdoCbl, and GTP/MgCl 2 in the GC-based assay (data not shown). Because HCM (5,23) from Methylibium petroleiphilum is very similar to the standalone ICM from Streptomyces cinnamonensis and catalyzes the interconversion of 3-hydroxybutyryl-CoA and 2-hydroxy- isobutyryl-CoA (5, 24), we decided to examine their substrate specificity overlap. However, conversion of DL-3-hydroxybutyryl-CoA to 2-hydroxyisobutyryl-CoA was not observed as judged by an HPLC-based assay (data not shown).…”

Development of materials and technologies for control of polymer recycling

“…106 PTMG overcomes some undesirable properties of PLLA such as low heat-resistance and racemization, which cause a decrease in crystallinity. PTMG was found to be a material having a higher melting point than 200 1C and a superior recyclability capable of being depolymerized controllably into cyclic dimer tetramethyl glycolide or methacrylic acid by using specific catalysts (Scheme 27).…”

Production of 2-Hydroxyisobutyric Acid from Methanol by Methylobacterium extorquens AM1 Expressing ( R )-3-Hydroxybutyryl Coenzyme A-Isomerizing Enzymes

“…It was classified as a coenzyme B 12 -dependent acyl-CoA mutase and shown to specifically isomerize 3-hydroxybutyryl-CoA into 2-hydroxyisobutyryl-CoA (3). On the basis of this reaction, the polyhydroxybutyrate (PHB) pathway, a prevalent overflow metabolic pathway of bacteria (6), could be employed for biotechnological 2-HIBA production (7). In this pathway (Fig.…”

“…The latter can readily be converted into methyl methacrylate, the precursor of poly-methyl methacrylate. This compound has a market size of more than 3 million tons per year, as it can be used for the production of acrylic glass, coating materials, and inks (1,7). Therefore, 2-HIBA has emerged as a target product of biorefinery processes.…”