Preservation of H(2) production activity in nanoporous latex coatings of Rhodopseudomonas palustris CGA009 during dry storage at ambient temperatures

To assess the applicability of latex cell coatings as an ‘off-the-shelf’ biocatalyst, the effect of osmoprotectants, temperature, humidity and O(2) on preservation of H(2) production in Rhodopseudomonas palustris coatings was evaluated. Immediately following latex coating coalescence (24 h) and for up to 2 weeks of dry storage, rehydrated coatings containing different osmoprotectants displayed similar rates of H(2) production. Beyond 2 weeks of storage, sorbitol-treated coatings lost all H(2) production activity, whereas considerable H(2) production was still detected in sucrose- and trehalose-stabilized coatings. The relative humidity level at which the coatings were stored had a significant impact on the recovery and subsequent rates of H(2) production. After 4 weeks storage under air at 60% humidity, coatings produced only trace amounts of H(2) (0–0.1% headspace accumulation), whereas those stored at < 5% humidity retained 27–53% of their H(2) production activity after 8 weeks of storage. When stored in argon at < 5% humidity and room temperature, R. palustris coatings retained full H(2) production activity for 3 months, implicating oxidative damage as a key factor limiting coating storage. Overall, the results demonstrate that biocatalytic latex coatings are an attractive cell immobilization platform for preservation of bioactivity in the dry state.