This line of research aims to recover organic matter from different types of wastewater and oily wastes to obtain a high-value-added product: polyhydroxyalkanoates (PHAs). PHAs are naturally occurring polymers that many microorganisms synthesize as carbon and energy reserves. Known as bioplastics, PHAs offer similar properties to those of conventional plastics, with the advantage of being biodegradable and synthesizable from renewable resources.
The main drawback associated with the large-scale production of PHAs is the high production costs, mainly due to the use of pure cultures and expensive substrates. As a solution, this research line focuses on the PHA production process based on the use of bacterial enrichments and waste(water) as substrates. This approach aims to reduce production costs by using more affordable, readily available substrates and transforming wastewater or oily waste into resources, thus improving the sustainability and economic viability of wastewater and oily waste management.
The idea of using bacterial enrichments and waste as substrates arose from the adaptive responses of microorganisms in biological wastewater treatment processes. In these processes, sources of the inoculum used, microorganisms are exposed to transient conditions, such as alternating periods of high and low substrate concentrations and aerobic and anaerobic environments. Under these unbalanced conditions, microorganisms have been shown to respond by producing PHAs.
The basis of the research is to exploit the ecological role of PHA as storage compounds by applying selective pressure that favors the growth of microorganisms with high storage capability. Sequencing batch reactors (SBRs) are used to establish microbial communities (phototrophic and chemolithotrophic heterotrophs) with high biopolymer-producing capacity.
In this research area, the group has focused its effort on the feasibility of using different industrial wastewaters (fish cannery effluents, crude glycerol from biodiesel production plants, cooking used oil...) as substrates for establishing PHA production processes. In particular, using waste oil as substrates alongside PHA has been demonstrated to yield triacylglycerides (TAG), another biopolymer that serves as a precursor in biodiesel production. Conditions to promote the accumulation of one over the other have been investigated using aerobic mixed cultures. Currently, one of our key goals is to develop biotechnology to convert used cooking oil into PHAs. This not only provides a sustainable and compact solution for managing waste oil, but also supports the production of biodegradable plastics.
Projects
· IGNICIA Valorización de residuos graxos para producir biopolímeros (PRETENACC) Programa Ignicia da Axencia Galega de Innovación da Xunta de Galicia. (017_IN855A_2023 (2024-2025)
· Integrative process development for biopolymer production through the valorisation of lipidic waste streams (ECOPOLYVER) Agencia Estatal de Investigación (Retos 2020. PID2020-112550RB-C21) (2021-2024)
· Development of a biotechnological process based on a single unit to obtain polyhydroxyalkanoates (PHA) from fatty wastes generated in industry (POLYGO1) NextGeneration EU, Strategic Projects Oriented to the Ecological and Digital Transition. (2022-2024)
Completed Projects
· Biorrefinería centralizada para la valorización de efluentes del sector transformador de pescado en forma de bioplásticos (BIOCENPLAS) Ministerio de Agricultura Pesca y Alimentación (Desarrollo tecnológico, la innovación y el equilibrio de la cadena decomercialización en el sector pesquero y de la acuicultura 2021. 2021-PN070) (2021-2023)
· Facing the treatment/recovery of saline wastewater to assure future water availability (TREASURE-TECHNOSALT)
Agencia Estatal de Investigación (Retos 2017. CTQ2017-83225-C2-1-R) (2018-2020)
· Sustainable system for the valorisation of fish canning wastewater for biopolymers production (FISHPOL)
Spanish Government.(CTQ2014-55021-R). (2015-2018)
Principal Researcher: A. Mosquera-Corral This project is focused on the valorisation of different liquid wastes by means of the utilization of mixed cultures to accumulate their organic carbon fraction present in these effluents in the form of polyhydroxyalkanoates (PHA) instead of the simple removal of these compounds in wastewater treatment processes. These accumulated compounds have different potential applications depending on their composition, such as bioplastics production, energy source or groundwater remediation.
The aim of this research work is to establish the optimum operational conditions to produce mixed cultures able to accumulate the PHA using liquid wastes like glycerol, from the biodiesel production process, characterized by the absence of ammonia content, and pre-acidified fish canning effluents containing ammonia. Furthermore these mixed cultures will be studied to achieve the operational conditions to reach the highest percentages of PHA accumulation with each substrate. Kinetic and stoichiometric parameters will be studied to obtain information regarding bioplastics productivity. Biomass enrichment and accumulation processes are highly dependent on the substrate composition. For this reason the effects of the use of different substrates and of the presence of potential inhibitors will be researched in the project. Experiments will be performed in lab-scale reactors and batch tests. In order to better understand the process the main bacteria populations contained in the obtained mixed culture will be identified by means of molecular techniques (FISH, DGGE, cloning). The composition of the produced storage compounds in the form of PHA such as polyhydroxybutyrate, valerate, etc. and also the occurrence of polyglucose accumulation will be studied to determine the possible applications of this stored bioplastics.
Furthermore obtained results will allow performing the calculation of the economic feasibility of different possible applications focused on the bioplastics production itself, the use of these accumulated compounds as energy resource to produce biogas and their use as organic carbon source for groundwater remediation to remove nitrogen oxides by denitrification.