The formation of 2,5-dimethyl-4-hydroxy-2H-furan-3-one by cell-free extracts of Methylobacterium extorquens and strawberry (Fragaria × ananassa cv. Elsanta)

The formation of 2,5-dimethyl-4-hydroxy-2H-furan-3-one (DMHF), using the bacterial cells of Methylobacterium extorquens (strain with CABI registration number: IMI 369321) and strawberry cells (Fragaria × ananassacv. Elsanta), was studied. A combined mixture of the bacterial cell-free extract plus the strawberry extract was used as the enzymatic source. The pH of all the experimental aliquots was pH 6.0. The studied substrates were short-chain alcohols, carbohydrates and one amino acid. DMHF was analyzed by HPLC with UV detection at 280 nm. When 1,2-propanediol, 1-propanol, sucrose and fructose were used as substrates, the best production rates of DMHF were achieved, having a combined mixture of the bacterium and strawberry (minus the achenes) as the enzymic source. On the other hand, glucose, 1,2-propanediol, 2-propanol and fructose were the best substrates for the production of DMHF when a combined mixture of the bacterium and achenes served as the enzymic source. All results were obtained by comparing the production of DMHF from the strawberry extract alone and the bacterium plus the strawberry, without the achenes (in the first case) and the production of DMHF from the achene extract alone and the bacterium plus the achenes (in the second case). Moreover, the dehydrogenation activities of these three enzyme sources were determined by measuring the absorption of NADH at 340 nm. The substrate which was used for this series of the experiments was 1,2-propanediol. These results indicate the undoubted cooperation between the plant and the bacterial cells. This paper reports, for the first time, the formation of DMHF by bacterial and plant cell-free extracts.