The invention relates to the microbial fermentation of gaseous substrates, particularly to gas/liquid contact modules and bioreactors configured to improve the efficiency of fermentations, particularly microbial fermentations of substrates comprising CO. In a particular embodiment, a gas/liquid contact module with multiple channels is configured to produce products in a liquid fermentation broth. In a further particular embodiment, there is provided a method of fermentation of a gaseous substrate to produce a product in a liquid fermentation broth.
