Valorization of agro-industrial fermentation residues: biotransformation of ginger active molecules

The ginger rhizome is a primary ingredient of oriental food, beverage, and herbal medicine catching on Western Countries meals. In 2016 the food sector processed 3.3 million tonnes of ginger generating a pulp waste that was mostly destined to agricultural field, biorefinery, papermaking etc.1 The ginger pulp waste still contains an oleoresin rich in gingerol-like compounds, such as gingerols and shogaols, bioactive components with recognized anti-inflammatory and anticancer properties.2,3 As an alternative valorisation strategy, the recovery of the main ginger waste components and their biotransformation to generate a small library of optically enriched derivatives was herein investigated. The oleoresin was first extracted from a fermented ginger biomass originating from a local farm. The conventional extraction confirmed the presence of still 30% gingerol-like compounds with unaltered chemical profile as characterized and quantified by UPLC-TUV and GC-MS. Then the enantioselective reduction of prochiral carbonyl moiety of pure isolated 6-gingerol (1), 8-gingerol (2), 6-shogaol (3), 8-shogaol (4), 6-paradol (5), 8-paradol (6) and zingerone (7) by different alcohol dehydrogenases (ADHs)4 was investigated. From our preliminary results, no ketone reduction was observed for 3 and 4. As far as the other substrates concern, only the ADH from Micrococcus luteus and engineered ADHs from Evoxx led to chiral alcohols in low yield, but with good diastereo- and enantiomeric excess (d.e and e.e) (Figure 1).