In the present study, 2 biocatalysts, namely carbohydrases and proteases, were assessed for organic matter solubilisation and methane yield enhancement of microalgae biomass. This study evidenced Chlorella vulgaris carbohydrate accumulation (40% on VSS basis) when grown in urban wastewater. Despite the carbohydrate prevailing fraction, protease pretreatment showed higher organic matter hydrolysis efficiency (54%). Microscopic observation revealed that carbohydrases affected slightly the cell wall while protease was not selective to wall constituents. Raw and pretreated biomass was digested at 1.5kgtCODm(-3)day(-1) organic loading rate (OLR1) and 20 days hydraulic retention time (HRT). The highest methane yield (137mLCH4gCODin(-1)) was achieved in the reactor fed with protease pretreated C. vulgaris. Additionally, anaerobic digestion was conducted at OLR2 (3kgtCODm(-3)day(-1)) and HRT (15days). When compared to raw biomass, methane yield increased 5- and 6.3-fold at OLR1 and OLR2, respectively. No inhibitors were detected during the anaerobic digestion.
Authors: Mahdy A, Ballesteros M, González-Fernández C. ;Full Source: Bioresource Technology. 2015 Aug 31. pii: S0960-8524(15)01186-4. doi: 10.1016/j.biortech.2015.08.080. [Epub ahead of print] ;