Cleaves the beta-1,4-linkages between beta-D-galactose and alpha-L-3,6-anhydro-galactose residues in agarose. Cleaves agarose in a random manner with retention of the anomeric-bond configuration, producing beta-anomers that give rise progressively to alpha-anomers when mutarotation takes place. Hydrolysis of (1->4)-beta-D-galactosidic linkages in agarose, giving the tetramer as the predominant product. Gut bacteria supply the human body with energy from dietary polysaccharides through glycosidases that are absent in the human genome. Beta-agarases, which are active on agarose from marine red algae of the genus Porphyra, are present in marine bacteria. They are absent from metagenome data of gut bacteria, except from the genome of the gut bacterium B.plebeius isolated from Japanese individuals. Seaweeds make an important contribution to the diet in Japan and Porphyra (nori) is the most important nutritional seaweed used to prepare sushi, suggesting that seaweeds with associated marine bacteria have been the route by which genes coding for beta-agarases have been transferred in human gut B.plebeius genome (PubMed:20376150 and PubMed:23150581). Belongs to the glycosyl hydrolase 16 family. A gut's tale - Issue 158 of March 2014