Exo-beta-1,3-glucanase that specifically hydrolyzes laminarin and laminarioligosaccharides, producing glucose and laminaribiose as end products. Successive hydrolysis of beta-D-glucose units from the non-reducing ends of (1->3)-beta-D-glucans, releasing alpha-glucose. kcat is 138 sec(-1) with L.digitata soluble laminarin as substrate (at pH 6 and 40 degrees Celsius). Optimum pH is 6. Maintains 70% or more of the maximal activity from pH 6.0 to 9.0. Optimum temperature is 50 degrees Celsius. Maintains 70% or more of the maximal activity from 35 to 65 degrees Celsius. Is up-regulated during growth on biomass, i.e. when the bacterium is grown on cellobiose, xylan, and various pretreated switchgrass samples. Belongs to the glycosyl hydrolase 55 family.