Abstract
Hydrogen offers a source of energy that does not produce any greenhouse gas when combusted. However, some manufacturing methods of hydrogen consume large amounts of energy and produce carbon dioxide as a by-product. The production of hydrogen by bacteria is an attractive alternative, because it is not energy intensive and - under the right conditions - does not release greenhouse gases. In this review, we introduce the five known ways by which bacteria can evolve hydrogen. We then describe methods to encapsulate living bacteria in synthetic layers, called coatings, for applications in bioreactors. We review the few examples in which biocoatings have been used to produce hydrogen via the photo-fermentation method. Although not used in biocoatings so far, the dark fermentation method of hydrogen production avoids the need for illumination while offering a high yield with low oxygen evolution. We identify the potential for using genetically-modified bacteria in future research on biocoatings.