Membrane-based harvesting processes for microalgae and their valuable-related molecules: A review

Producción CientíficaThe interest in microalgae production deals with its role as the third generation of feedstock to recover renewable energy. Today, there is a need to analyze the ultimate research and advances in recovering the microalgae biomass from the culture medium. Therefore, this review brings the current research developments (over the last three years) in the field of harvesting microalgae using membrane-based technologies (including microfiltration, ultrafiltration and forward osmosis). Initially, the principles of membrane technologies are given to outline the main parameters influencing their operation. The main strategies adopted by the research community for the harvesting of microalgae using membranes are subsequently addressed, paying particular attention to the novel achievements made for improving filtration performance and alleviating fouling. Moreover, this contribution also gives an overview of the advantages of applying membrane technologies for the efficient extraction of the high added-value compounds in microalgae cells, such as lipids, proteins and carbohydrates, which together with the production of renewable biofuels could boost the development of more sustainable and cost-effective microalgae biorefineries.Tecnológico de Monterrey (Facultad de Ciencias e Ingeniería y Centro de Biotecnología FEMSA) - (Grupo Focal Bioprocesos 0020209I13)Agencia Nacional Polaca para el Intercambio Académico (NAWA) - (Agreement PPN/ULM/2020/1/00005/U/00001

Continuous lactate-driven dark fermentation of restaurant food waste: Process characterization and new insights on transient feast/famine perturbations

Producción CientíficaThe effect of hydraulic retention time (HRT) on the continuous lactate-driven dark fermentation (LD-DF) of food waste (FW) was investigated. The robustness of the bioprocess against feast/famine perturbations was also explored. The stepwise HRT decrease from 24 to 16 and 12 h in a continuously stirred tank fermenter fed with simulated restaurant FW impacted on hydrogen production rate (HPR). The optimal HRT of 16 h supported a HPR of 4.2 L H2/L-d. Feast/famine perturbations caused by 12-h feeding interruptions led to a remarkable peak in HPR up to 19.2 L H2/L-d, albeit the process became stable at 4.3 L H2/L-d following perturbation. The occurrence of LD-DF throughout the operation was endorsed by metabolites analysis. Particularly, hydrogen production positively correlated with lactate consumption and butyrate production. Overall, the FW LD-DF process was highly sensitive but resilient against transient feast/famine perturbations, supporting high-rate HPRs under optimal HRTs.European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 894515MCIN/AEI /10.13039/501100011033 - Unión Europea NextGenerationEU/PRTR (Grant RYC2021‐034559‐I)Junta de Castilla y León - EU-FEDER (CLU 2017-09, CL-EI-2021-07 y UIC 315

Elucidating the role of pH and total solids content in the co-production of biohydrogen and carboxylic acids from food waste via lactate-driven dark fermentation

Producción CientíficaNotwithstanding lactate-driven dark fermentation (LD-DF) can cope with inhibition issues associated with the over-proliferation of lactate producers, there is still a knowledge gap about the role of key operational parameters. In this study, the effect of pH and total solids (TS) content on the co-production of hydrogen and carboxylic acids, including medium-chain carboxylic acids (MCCAs), from food waste (FW) via LD-DF was investigated. A series of batch fermentations was conducted, first, without pH control, and then at fixed pH values of 5.5, 6.0 and 6.5, while maintaining constant the TS content at 5 %. It was observed that the higher the operational pH, the lower the accumulation of lactate and the higher the extent and rate of hydrogen production, sustaining a maximum hydrogen production yield and rate of 81 NmL/g VS fed and 9 NL/L-d, respectively, at pH 6.5. In a second series of batch tests, the TS content was adjusted to 5, 7.5 and 10 % while pH was set at 6.5. The highest hydrogen production performance (103 NmL/g-VS fed and 13.3 NL/L-d) was achieved at 7.5 % TS, which also resulted in the highest accumulation of MCCAs, particularly of caproate, with an associated titer of 8.7 g/L. Hydrogen production plateaued with the exhaustion of lactate regardless of the condition tested. Further assessment through biochemical methane potential tests showed that LD-DF effluents can be alternatively valorised into biogas. Overall, the results obtained confirmed the key role of pH and TS content in the LD-DF of FW and suggested that this non-conventional route may be an alternative approach to cope with lactate flux diverted toward undesirable non-hydrogen-producing metabolic pathways.European Commission-H2020-MSCA-IF-2019 project UP-GRAD (894515)Junta de Castilla y León y EU-FEDER (program CLU 2017-09, CL-EI-2021-07, and UIC 315

A Comprehensive Overview of the Potential of Tequila Industry By-Products for Biohydrogen and Biomethane Production: Current Status and Future Perspectives

Nowadays, the use of agro-industrial by-products as alternative sustainable resources to generate bioenergy and high-value bioproducts is one of the most important research topics to tackle environmental concerns related to the excessive consumption of fossil-based fuels and rapid urbanization and industrialization. This chapter provides a broad overview of the potential of the main tequila industry by-products, agave bagasse and tequila vinasse, for biohydrogen (bioH2) and biomethane (bioCH4) production via dark fermentation and anaerobic digestion, respectively. First, pretreatment or conditioning steps commonly applied to tequila by-product streams before downstream biological processes are highlighted. The operational performance of bioH2- and bioCH4-producing reactors is subsequently reviewed, with a focus on reactor configuration and performance, microbial metabolic pathways, and the characterization of microbial communities. Additionally, the development of multi-stage anaerobic digestion processes is comprehensively discussed from a practical point of view. Finally, limitations and potential improvements in the field of bioH2 and bioCH4 production are presented

Unlocking the high-rate continuous performance of fermentative hydrogen bioproduction from fruit and vegetable residues by modulating hydraulic retention time

Producción CientíficaHarnessing fruit-vegetable waste (FVW) as a resource to produce hydrogen via dark fermentation (DF) embraces the circular economy concept. However, there is still a need to upgrade continuous FVW-DF bioprocessing to enhance hydrogen production rates (HPR). This study aims to investigate the influence of the hydraulic retention time (HRT) on the DF of FVW by mixed culture. A stirred tank reactor under continuous mesophilic conditions was operated for 47 days with HRT stepwise reductions from 24 to 6 h, leading to organic loading rates between 47 and 188 g volatile solids (VS)/L-d. The optimum HRT of 9 h resulted in an unprecedented HPR from FVW of 11.8 NL/L-d, with a hydrogen yield of 95.6 NmL/g VS fed. Based on an overarching inspection of hydrogen production in conjunction with organic acids and carbohydrates analyses, it was hypothesized that the high FVW-to-biohydrogen conversion rate achieved was powered by lactate metabolism.European Commission-H2020-MSCA-IF-2019 project UP-GRAD (894515)Junta de Castilla y Leon - FEDER (program CLU 2017-09, CL-EI-2021-07 & UIC 315

Influence of key operational parameters on biohydrogen production from fruit and vegetable waste via lactate-driven dark fermentation

Producción CientíficaThis study aims at investigating the influence of operational parameters on biohydrogen production from fruit-vegetable waste (FVW) via lactate-driven dark fermentation. Mesophilic batch fermentations were conducted at different pH (5.5, 6.0, 6.5, 7.0, and non-controlled), total solids (TS) contents (5, 7, and 9%) and initial cell biomass concentrations (18, 180, and 1800 mg VSS/L). Higher hydrogen yields and rates were attained with more neutral pH values and low TS concentrations, whereas higher biomass densities enabled higher production rates and avoided wide variations in hydrogen production. A marked lactate accumulation (still at neutral pH) in the fermentation broth was closely associated with hydrogen inhibition. In contrast, enhanced hydrogen productions matched with much lower lactate accumulations (even it was negligible in some fermentations) along with the acetate and butyrate co-production but not with carbohydrates removal. At pH 7, 5% TS, and 1800 mg VSS/L, 49.5 NmL-H2/g VSfed and 976.4 NmL-H2/L-h were attained.Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (grants CLU 2017-09, CL-EI-2021-07 and UIC 315

Dark fermentation process response to the use of undiluted tequila vinasse without nutrient supplementation

Producción CientíficaThe technical feasibility of valorizing tequila vinasse (TV), a wastewater with high pollution potential, through the production of biogenic hydrogen via dark fermentation, has long been proven in diverse lab-scale reactors that were operated either in batch or continuous mode. However, such systems have mainly been tested with diluted streams and nutrient supplementation, hindering the techno-economic attractiveness of the TV-to-hydrogen concept at large scale. In this study, the feasibility of producing hydrogen from high-strength undiluted TV with no added extra nutrients was evaluated under batch mesophilic conditions. Additionally, the use of two different acidogenic inocula obtained either by heat or heat-aeration pretreatment was investigated to get a greater understanding of the effect of inoculum type on the process. The results obtained showed that the TV utilized herein contained macro- and micro-nutrients high enough to support the hydrogenogenic activity of both cultures, entailing average hydrogen yields of 2.4–2.6 NL H2/L vinasse and maximum hydrogen production rates of 1.4–1.9 NL H2/L-d. Interestingly, the consumption of lactate and acetate with the concomitant production of butyrate was observed as the main hydrogen-producing route regardless of the inoculum, pointing out the relevance of the lactate-driven dark fermentative process. Clostridium beijerinckii was ascertained as key bacteria, but only in association with microorganisms belonging to the genera Enterobacter and Klebsiella, as revealed by phylogenetic analyses.Consejo Estatal de Ciencia y Tecnología de Jalisco (COECYTJAL; 8872–2020)

Recent trends and advances in biogas upgrading and methanotrophs-based valorization

Producción CientíficaThe global quest for sustainability in industrial activities and waste management has recently boosted biogas production worldwide. However, the rapid decrease in the levelized cost of electricity of renewable energies will soon entail electricity prices from biogas much higher than those from solar or wind power. In this context, the upgrading of biogas into biomethane represents an alternative to on-site biogas combustion. Membrane separation technology is rapidly dominating the biogas upgrading market and displacing scrubbing and adsorption technologies driven by the recent breakthroughs in material science. Similarly, biogas biorefineries have recently emerged as an innovative platform for biogas valorization capable of biotransforming methane into added value products. The limited number of bioproducts naturally synthesized by methanotrophs can be boosted via metabolic engineering of methanotrophs, while novel bioreactor configurations capable of supporting a cost-effective methane mass transfer from the gas phase to the methanotrophic broth are currently under investigation to facilitate the full scale implementation of biogas biorefineries.Junta de Castilla y Leon - FEDER (program CLU 2017–09, CL-EI-2021–07 and UIC 315)European Commission-H2020-MSCA-IF-2019 project UP-GRAD (894515)Ministerio de Ciencia, Innovación y Universidades (project IJC2019–040495-I

Phenol and nitrogen removal in microalgal‐bacterial granular sequential batch reactors

Producción CientíficaBACKGROUND The microalgal-bacterial systems work on the principle of the symbiotic relationship between algae and bacteria. The ability of algal-bacterial photobioreactors for the treatment of wastewater containing ammonia and phenol has been poorly addressed. In this work a self-sustaining synergetic microalgal-bacterial granular sludge process was thus developed to treatment of industrial wastewater based upon the low cost of photosynthetic oxygenation and the simultaneous phenol and nitrogen removal. The performance of a conventional sequential batch reactor (SBR) based on aerobic bacterial communities (SBRB) and a microalgal-bacterial granular SBR (SBRMB) were comparatively assessed. The major challenges associated with microalgal-bacterial systems have been discussed. RESULTS A complete removal of phenol (100 mg L-1) was achieved in both reactors. The reactors SBRB and SBRMB showed similar performance in term of removal of inorganic nitrogen. Nitrogen mass balances estimated nitrogen assimilation, nitrification and denitrification. Higher simultaneous nitrification and denitrification (70% SND) occurred in SBRB as determined by mass balances. The higher nitrogen assimilation (17.9%) by the microalgal-bacterial biomass compensated the lower denitrifying activity in SBRMB (54% SND), resulting in a removal of inorganic nitrogen (61%) similar to that obtained in SBRB (66%). N2O was not detected in the headspace of any system. CONCLUSIONS Granular microalgae-bacterial consortia implemented in SBR constitute an efficient method for industrial wastewater treatment achieving complete removal of ammonia and phenol. The application of SBRMB would be more cost-effective than SBRB mainly due to the significant energy savings in SBRMB resulting in a sustainable system that contributes to the circular bioeconomy.Junta de Castilla y León y la UE-FEDER (grant numbers CLU 2017-09, CL-EI-2021-07 and UIC 315

Integrated ozonation-enzymatic hydrolysis pretreatment of sugarcane bagasse: enhancement of sugars released to expended ozone ratio

Producción CientíficaThe combined effects of three key ozonation process parameters on the integrated ozonation-enzymatic hydrolysis pretreatment of sugarcane bagasse (SCB) were investigated, with emphasis on the relationship between sugar release and ozone consumption. A lab-scale fixed bed reactor was employed for ozonation at varying ozone doses (50, 75 and 100 mg O3/g SCB), particle sizes (420, 710 and 1000 µm) and moisture contents (30, 45 and 60% w/w) in multifactorial experiments, keeping a residence time of 30 min. The ozonated SCB showed a reduction in the content of acid-insoluble lignin from 26.6 down to 19.1% w/w, while those of cellulose and hemicellulose were retained above 45.5 and 13.6% w/w, with recoveries of 100–89.9 and 83.5–72.7%, respectively. Ozone-assisted enzymatic hydrolysis allowed attaining glucose and xylose yields as high as 45.0 and 37.8%, respectively. The sugars released/ozone expended ratio ranged between 2.3 and 5.7 g sugars/g O3, being the higher value achieved with an applied ozone input of 50 mg O3/g SCB and SCB with 420 µm particle size and 60% moisture. Such operating conditions led to efficient ozone utilization (<2% unreacted ozone) with a yield of 0.29 g sugars/g SCB. Overall, the amount of sugars released relative to the ozone consumed was improved, entailing an estimated cost of ozonation of USD 34.7/ton of SCB, which could enhance the profitability of the process.Consejo Nacional de Ciencia y Tecnología (CONACYT) - (Project-CB-SEP-133791