NOVELTY - Method (M1) for selecting or identifying a bacterium, involves (a) providing a sample comprising bacteria, (b) subjecting the sample to a repeated irradiation treatment and (c) isolating from the treated sample, a bacterium which has the ability to live or grow in presence of lignin, cellulose and/or xylan as a carbon source.    USE - The method is useful for selecting or identifying bacterium chosen from Deinococcus, Bacillus, Microbacterium, Cellulosimicrobium, Methylobacterium, Sphingobacterium, Pseudomonas, Caldimonas, Paenibacillus, Gordonia, Rhodococcus, Stenotrophomonas, Novosphingobium, Sphingomonas, Flavobacterium, Sphingobium, Sphingopyxis, and Porphyrobacter in sample chosen from an environmental sample, preferably soil, water, hot springs, marine environment, mud, wood, stone, moss, vegetal extract, lichen, sediment, peatlands, biofilm, industrial effluents, gas, sand, oil, sewage, animal and human excrements. The bacterium is useful for producing bioenergy products or metabolites from lignocellulosic biomass (claimed).    ADVANTAGE - The method is cost-effective and improves the viability, growth and functions of the bacterium.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) isolated bacterium, or its extract obtained by the above-mentioned method, where the bacterium has the ability to grow in presence of lignin as sole carbon source at 30 degrees C and resist an UV treatment of 4 mJ/cm2 or the bacterium has the ability to utilize cellulose and xylan as carbon source at 30 degrees C and resist an UV treatment of 4 mJ/cm2;    (2) method (M2) for degrading lignocellulosic biomass into fermentable sugars, involves exposing lignocellulosic biomass to a bacterium or its extract;    (3) method (M3) for producing bioenergy products or metabolites, involves exposing lignocellulosic biomass to a bacterium or its extract, to produce fermentable sugars, and fermenting the sugars into bioenergy products or metabolites; and    (4) reactor or fermentor comprising lignocellulosic biomass and the above-cited bacterium or its extract.