production process long and expensive. One possible alternative would be working with microbial communities, which makes the process shorter, and cheaper. However, process control is much more difficult when working with bacterial communities than when applying enzymatic solutions. General applications In the early 1980s, enzymes produced by fibrolytic bacteria were incorporated in cattle food. This allowed them to obtain more energy from the forage which they fed on, thanks to the partial digestion of lignocellulosic material. They have been gaining importance in the food processing industry, in the filtration of fruit and vegetables juices, in edible oil extraction, in baking, etc. Furthermore, the use of these kinds of enzymes was progressively extended to the textile and laundry industry, where they are used to fade the intense blue of fabrics and to provide them a more faded appearance. In the chemical industry, these enzymes have allowed the development of new detergents and washing-up liquids; in the paper industry they play a very important role in bleaching processes, minimizing toxicity and being more economic; and in biotechnological research, the use of the cellulose binding domains from fibrolytic enzymes has allowed the purification of recombinant proteins. Energy applications Fibrolytic bacteria are expected to play an important role in renewable energy production through biomass degradation. One of the main objectives of biotechnology is biofuel production with the aim to reduce emissions, because biofuels obtained from plant material does not contribute a net atmospheric input of . The gas emitted during the combustion of biofuels of cellulolytic origin will be reabsorbed in vegetable growth and this is why it does not have an environmental impact so negative. Discovery of fibrolytic genes and fibrolytic bacteria Probably, the best studied fibrolytic community is the one in the rumen of ruminants. However, there are other organisms that are able to degrade vegetable fibres, from insects to mollusks, all of them can do it thanks to the activity of different microbial symbionts. In order to improve the industrial transformation processes of vegetable fibres and related applications it is necessary to discover new and efficient enzymes and specialized bacterial communities. Next we describe the main steps in the discovery of genes and genomes from fibrolytic bacteria . The first step that can be followed to obtain fibrolytic bacteria from gastrointestinal cavities in ruminants is the culture of the target communities inside the rumen of a cow by introducing a nylon