Search

Biogas, a gaseous effluent from the anaerobic digestion of organic waste, is considered an important source of energy, since it has a composition mainly of methane (CH 4 ; 55-75%) and CO 2 (20-60%). Today, CO 2 from biogas is an excellent carbon source to induce high microalgal biomass production; however, each microalga strain can have different optimal CO 2 concentrations for maximizing their bio-refinery capacity as well as different ability to endure stressful conditions of industrial effluents. This study assessed the bio-refinery capacity of Chlorella sp. and Scenedesmus sp., native of Lago de Chapala, Mexico, from biogas, as well as the effect of high CO 2 and methane concentrations on the physiological performance to grow, capture CO 2 and biochemical composition of both microalgae cultured under different biogas compositions. The results show that both microalgae have the biotechnological potential to endure biogas compositions of 25% CO 2 -75% CH 4 . Under this condition, the biomass production attained by Chlorella sp. and Scenedesmus sp. was 1.77 ± 0.32 and 2.25 ± 0.20 g L -1 , respectively, with a biochemical composition mainly of carbohydrates and proteins. Overall, this study demonstrates that both microalgae have the ability to endure the stressful biogas composition without affecting their physiological capacity to capture CO 2 and biosynthesize high-value metabolites. Moreover, it is worth highlighting the importance of screening wild-type microalgae from local ecosystems to determine their physiological capacity for each biotechnological application.

Microalgae are considered as a promising biotechnological strategy to capture CO 2 from biogas, producing biomass with valuable energetic compounds. This study has evaluated the biotechnological potential to fix CO 2 from biogas and biomass production by Scenedesmus obliquus cultured in four different formulations of culture media, C30, Bristol, Bold 3N, and C30+M, as well as the effect of methane (CH 4 ) of biogas during CO 2 fixation and biomass production. The results obtained showed that different nutrient composition and concentration of culture media, mainly micronutrient and vitamin concentrations, induced different patterns of CO 2 fixation from biogas and biomass production in S. obliquus. The highest CO 2 fixation (23.03 ± 0.24%) and biomass production (4.63 ± 0.31 g L -1 ) were attained in the microalgae growing in C30+M medium, accumulating mainly proteins. Moreover, these results demonstrated that the CH 4 of biogas did not affect CO 2 fixation from biogas and biomass production by S. obliquus. Overall, these results demonstrated that a culture medium with a balanced nutrient supply is crucial to increasing the biotechnological potential of microalgae to fix CO 2 from biogas.

An artificial neural network (ANN) was implemented to model the light profile pattern inside a photobioreactor (PBR) that uses a toroidal light arrangement. The PBR uses Tequila vinasses as culture medium and purple non-sulfur bacteria Rhodopseudomonas palustris as biocatalyzer. The performance of the ANN was tested for a number of conditions and compared to those obtained by using deterministic models. Both ANN and deterministic models were validated experimentally. In all cases, at low biomass concentration, model predictions yielded determination coefficients greater than 0.9. Nevertheless, ANN yielded the more accurate predictions of the light pattern, at both low and high biomass concentration, when the bioreactor radius, the depth, the rotational speed of the stirrer and the biomass concentration were incorporated in the ANN structure. In comparison, most of the deterministic models failed to correlate the empirical data at high biomass concentration. These results show the usefulness of ANNs in the modeling of the light profile pattern in photobioreactors.