Dark fermentation is one of the most attractive experimental methods for generating clean biofuel. In dark fermentation, bacteria convert carbohydrates into hydrogen gas and other energy-rich small molecules. The problem is that this process tends to produce relatively small amounts of biohydrogen. To find ways to boost efficiency, researchers recently examined the cast of microbial characters that participate in dark fermentation. The team discovered two distinct patterns of fermentation. At low pH (4.0 and lower), lactate and ethanol were the main fermentation products, with most of the work carried out by bacteria belonging to the groups Lactobacillus, Bifidobacterium, Leuconostoc, and Fructobacillus. At slightly higher pH (5.0 – 6.0), butyrate was the dominant product, generated largely by bacteria from the groups Clostridium, Lactobacillus, Bifidobacterium, and Prevotella. This butyrate pathway is believed to be more favorable for generating hydrogen and was found to involve a more diverse community of bacteria. These findings could help scientists better understand the processes inside bioreactors and lead to more efficient methods of producing biofuel from waste.