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We identified a novel flavoprotein–cytochrome ccomplex d-gluconate dehydrogenase (GADH) encoded by gndXYZof Gluconobacter oxydansNBRC 3293, which is phylogenetically distinct from previously reported GADHs encoded by gndFGHand gndSLCof Gluconobacterspp. To analyze the biochemical properties of respective GADHs, Gluconobacter japonicusNBRC 3271 mutant strain lacking membranous d-gluconate dehydrogenase activity was constructed. All GADHs (GndFGH, GndSLC, and GndXYZ) were successfully overexpressed in the constructed strain. The optimal pH and KMvalue at that pH of GndFGH, GndSLC, and GndXYZ were 5, 6, and 4, and 8.82 ± 1.15, 22.9 ± 5.0, and 11.3 ± 1.5 m m, respectively. When the mutants overexpressing respective GADHs were cultured in d-glucose-containing medium, all of them produced 2-keto-d-gluconate, revealing that GndXYZ converts d-gluconate to 2-keto-d-gluconate as well as other GADHs. Among the recombinants, the gndXYZ-overexpressing strain accumulated the highest level of 2-keto-d-gluconate, suggesting its potential for 2-keto-d-gluconate production.Graphical AbstractThe 3 phylogenetically distinct GADHs of Gluconobacterspp. convert d-gluconate to 2-keto-d-gluconate but show the different biochemical properties.

Ability of poly (styrene-alt-maleic anhydride) (PSMA) to undergo a conformational transition into an amphipathic α-helix coil offers one possible mechanism by which PSMA surface activity can be switched on or off in response to the pH change. This behaviour allows it to be useful in membrane solubilization for extraction technology. Bioactive compounds are recovered from plant tissues for different reasons. One of the most important reasons is due to the increased demand in nutraceuticals market and modern therapeutics. Despite this, aqueous-based extraction of these compounds has been reported to give low extraction yield. A development of new green extraction protocol is still a challenging task for all researchers nowadays. This study demonstrated, for the first time, possible use of PSMA as a lysis agent for plant bioactive compound extraction. To enhance its membrane affinity at physiological pH, the polymer was esterified with methanol. Both PSMA and its derivative (ePSMA) were characterized in terms of their membrane binding affinity through a combined use of both surface characterization and physical techniques. Analysis of the ternary phase diagrams suggested that ePSMA could facilitate stronger hydrophobically-driven interactions with the lipid. This was convinced by the reduced critical PSMA/lipid mass ratio from 7:1 (PSMA) to 1:1 (ePSMA), as observed in the ternary phase diagrams. Last but not the least, the crude extracts of Coffea robusta leaves obtained from ePSMA-based extraction showed a total phenolic content of 20.32±0.75 mg/g sample, significantly higher than that from the PSMA- (14.24±1.27 mg/g sample) and aqueous-based (16.33±1.03 mg/g sample) extractions. A structural manipulation of PSMA is thus a key to tailor its membrane solubilization and so, the extraction efficacy of bioactive compounds from plant cells.