NOVELTY - Rational mining for induced enzyme in microbial communities involves a) providing at least one community of microorganisms, b) cultivating microbial populations of at least one community in at least one container under conditions to eliminate matter deriving from the natural habitat and to allow the microbial community to reach a metabolic steady-state, c) removal from at least one container of step (b) of at least one fraction of microorganisms, and transfer of at least one fraction into at least two separate containers.    USE - For rational mining for induced enzymes in microbial communities and production of enzymes (claimed) which is used as high-performing biological catalysts, or applications in industrial and environmental biotechnology, production of renewable energy from biobased feedstocks, production of biogas, production of bioethanol, food/feed industry, dairy industry, baking industry, wine and fruit juice industry, brewing industry, textile industry, leather industry, applications in detergents, pulp and paper industry, processing of fats and oils, application as digestive aid, chemical synthesis and for degradation of harmful compounds at contaminated sites or at waste water treatment plants.    ADVANTAGE - The method enables a rational way of inducing, finding and identifying enzymes for diverse areas. Using the information from this analysis it is possible to derive the DNA sequence and to clone or construct the gene in order to produce the enzyme for further tests regarding activity, stability, pH- and temperature optimum. It is further possible to use the DNA sequence for production of the enzyme/enzymes in a host organism or the original organism on an industrial scale, e.g. for use in any of the earlier described processes. Thus, by using the method it is not only possible to find and produce new enzymes with properties superior to those of already known enzymes but also to identify new unique enzymes never used industrially by man since the whole microbial population is used as a source. The methods enables rational enzyme mining in microbial communities and the resulting gels represents the meta-secretome from an active microbial community. The gels are of high enough quality to be subjected to image analysis and identification of differences in protein expression pattern and/or expression strength between the induced and non-induced culture. Even without advanced image analysis tools it is possible to identify spots that differs in strength between the two gels. Identified spots are then subjected to further analyses, whereas those spots that do not differ can be excluded, which dramatically will reduce the time and effort associated with cloning and screening of all the proteins.    DETAILED DESCRIPTION - A method (M1) for rational mining for induced enzyme in microbial communities involves a) providing at least one community of microorganisms, b) cultivating the microbial populations of at least one community in at least one container under conditions, where the microorganisms are given a defined culturing medium, to eliminate matter deriving from the natural habitat and to allow the microbial community to reach a metabolic steady-state, c) removal from at least one container of step (b) of at least one fraction of microorganisms, and transfer of at least one fraction into at least two separate containers, d) providing at least one of the fractions of microorganisms from step (c) with a defined medium which includes an inducing substance and/or a substance against which enzyme is desired, to induce a regulation of expression of the desired enzyme, and at least one of the other fraction from step (c) with a defined medium without inducing substance and without substance against which enzyme is desired for the purpose of comparison, and maintaining and/or cultivating the fractions of microorganisms, and e) withdrawing and analyzing samples of at least one induced fraction and at least one non-induced fraction of step (d) for identification of the induced enzyme/enzymes. An INDEPENDENT CLAIM is included for a method (M2) for rational mining for induced enzyme/enzymes in microbial communities and its production involving carried out steps (a)-(d), followed by e) withdrawing and analyzing samples of at least one induced fraction and one non-induced fraction of step (d) for identification of the induced enzyme, f) analyzing the identified enzyme, deriving the DNA sequence that codes for the enzyme, and h) producing the identified enzyme by use of a host organism or the original parental organism.