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Papers by Teresa Gea

L'objectiu principal del present projecte és l'obtenció d'un simulador, basat en un model estruct... more L'objectiu principal del present projecte és l'obtenció d'un simulador, basat en un model estructurat, que permeti optimitzar les condicions del procés de compostatge de llots de depuradora, així com predir-ne l'evolució. L'esmentat simulador i el model associat hauran de ser aplicables al compostatge d'altres residus orgànics com la fracció orgànica de residus municipals, els residus ramaders i, en general, les mescles de residus de composició coneguda (cocompostatge). L'esmentada optimització es considera en dos nivells: a) la millora de l'efi ciència del procés per a l'obtenció d'un compost de qualitat estabilitzat i higienitzat; i b) la minimització dels impactes ambientals del procés, en especial les emissions a l'atmosfera d'amoníac i el consum energètic associat. Alhora, i per millorar el caràcter universal del model ja desenvolupat en les fases prèvies del projecte, es planteja l'estudi detallat de les interaccions microbianes que es produeixen durant el procés com una nova línia de treball. Actualment, es troba disponible una primera versió simplifi cada del simulador, i s'estan realitzant els treballs corresponents per millorar-lo, perquè permeti la integració de fenòmens fi sicoquímics i biològics.

Resumen: Se considera que, durante los últimos años, el compostaje se ha establecido como una de ... more Resumen: Se considera que, durante los últimos años, el compostaje se ha establecido como una de las más prometedoras tecnologías para el tratamiento de residuos sólidos de elevado contenido orgánico, permitiendo reciclar dichos residuos en un abono de calidad ...

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Energies

Sophorolipids (SLs) are microbial biosurfactants with an important role in industry and a continu... more Sophorolipids (SLs) are microbial biosurfactants with an important role in industry and a continuously growing market. This research addresses the use of sustainable resources as feedstock for bioproducts. Winterization oil cake (WOC) and molasses are suitable substrates for SLs via solid-state fermentation (SSF). The model proposed herein was established for annually processing 750 t of WOC and comparing three support materials: wheat straw (WS), rice husk (RH), and coconut fiber (CF). Production capacity ranged 325–414 t of SLs per year. Unit Production Cost was 5.1, 5.7, and 6.9 USD/kg SL for WS, RH, and CF production models, respectively, and was slightly lower with other substrates. Financial parameters were CAPEX 6.7 MM USD and OPEX 1.9 MM USD/y, with a NPV, IRR and payback time of 6.4 MM USD, 31% and 3.2 y, respectively. SLs recovery from the solid matrix was the major contributor to operating costs, while fermentation equipment shaped capital costs. Results show that the phy...

Waste and Biomass Valorization, 2021

To improve the financial sustainability and business management of composting facilities, mostly ... more To improve the financial sustainability and business management of composting facilities, mostly small-scale and manually operated facilities, the simultaneous optimization of the process and quality of the final product must be prioritized. This study used artificial neural networks (ANNs) and particle swarm optimization (PSO) as tools to evaluate the composting of biowaste (BW) with different cosubstrates (i. star grass (SG) and ii. a SG and sugarcane filter cake (SFC) mixture). The simulation aimed to maximize product quality in the shortest processing time by varying the mixing ratio and turning frequency. The simulation showed optimal conditions with a turning frequency of twice per week with the following mixtures: (i) BW:SG (72.9:27.1), 76 days of processing; and (ii) BW:SFC:SG (60:16:24), 88 days of processing. The results showed the effect of the type of carbon source in the cosubstrates on the retention time, which may imply the need for a larger area in composting facilities. On the other hand, the findings show that a minimum time is required to achieve a product that meets quality standards, although a longer processing time reduces the agricultural value of the compost. This model can be used to define design criteria and operating conditions and select a cosubstrate that can contribute to improving the agricultural quality of the final product.

Biosurfactants are being proposed as a substitute for surfactants in the framework of a circular ... more Biosurfactants are being proposed as a substitute for surfactants in the framework of a circular economy strategy. Sophorolipids (SL) are a type of biosurfactant produced by yeast that can be produced through submerged or solid-state fermentation (SSF) processes. Even though sophorolipids are being produced at full scale, through submerged fermentations, environmental and technoeconomic information regarding its production through SSF is unavailable. An inventory of data necessary to perform preliminary economic and environmental assessments is presented in this study. Data was obtained from three SSF processes at 22-L reactor volume and from two SSF processes at 100-L reactor volume, using winterization oil cake and molasses as substrates, wheat straw as support material, and Starmerella bombicola as SL producing yeast. The effect of increasing the operation scale was assessed. Besides presenting parameters such as inoculum production, initial mass of substrates, and airflow requir...

Biochemical Engineering Journal, 2020

Abstract A novel aeration strategy has been developed at lab and bench-scale for Bacillus thuring... more Abstract A novel aeration strategy has been developed at lab and bench-scale for Bacillus thuringiensis (Bt) derived biopesticides production through solid-state fermentation, using a mixture of digestate and biowaste as substrates. A Box-Behnken design was performed to select key parameters of the spore production process, being temperature and biodegradability the factors with a significant effect. Further tests confirmed the importance of oxygen content for spore production. Thus, a two-stage aeration strategy consisting of a microaeration phase followed by a high-rate aeration period was developed and tested. The production strategy was validated in a 22-L reactor using two different strains (Bt kusrtaki, Btk, and israelensis, Bti), demonstrating the robustness of the protocol. Maximum production of 1.3 × 108 spores g-1 dry matter for Btk and 4 × 108 spores g-1 dry matter for Bti were obtained, representing a final yield of 5 and 29 spores produced per initial CFU, respectively.

Acidogenic fermentation of wastes produces volatile fatty acid (VFA)-rich streams that can be use... more Acidogenic fermentation of wastes produces volatile fatty acid (VFA)-rich streams that can be used as low-cost carbon sources for polyhydroxyalkanoate (PHA) production. In this study, an inoculum collected from an anaerobic reactor of a municipal WWTP was conditioned to suppress methanogenic activity. The heat-shock conditioning method of the inoculum proved to be more efficient than acid and alkaline conditioning methods for methanogen inhibition. Then, the pre-conditioned inoculum was used to determine the acidogenic potential of different wastes: three waste activated sludge (WAS) samples generated at different sludge retention times (SRTs, 2, 7 and 14 days), olive mill wastewater (OMW), glycerol, apple pomace (AP) and winterization oil cake (WOC). Batch tests were performed in quintuplicate at 37°C and pH 7. A higher degree of acidification was observed for high-rate activated sludge (2 days of SRT) (69%), followed by olive mill wastewater (OMW) (43%), while the lowest was for g...

Biomass Conversion and Biorefinery, 2020

Waste and Biomass Valorization, 2020

Abstract This study explores 9 different biomaterials (agro-wastes) and inert materials, to be us... more Abstract This study explores 9 different biomaterials (agro-wastes) and inert materials, to be used as support in SSF to produce sophorolipids (SLs) with Starmerella bombicola ATCC 22214. Winterization oil filtration cake and sugar beet molasses were the substrates. Biomaterials (lignocellulosic wastes or organic by-products) performed better than inert materials (perlite and polyurethane foams). High yields were obtained for rice husk (0.15 g SLs g −1 DM) and wheat straw (0.20 g SLs g −1 DM). Lactonic C18:1 predominates over acidic form in the mixture of SLs. The characterization of the process through a time course experiment shows that wheat straw is the best material to produce SLs. A proportional correlation between SLs yield and cumulative oxygen consumption was found, suggesting that cumulative oxygen content (COC) can be used as an indirect measure to monitor the SLs production. Graphic abstract

Journal of Surfactants and Detergents, 2019

Frontiers in Sustainable Food Systems, 2019

Solid-state fermentation (SSF) is, by definition, a technology carried out in absence or near abs... more Solid-state fermentation (SSF) is, by definition, a technology carried out in absence or near absence of free water. Therefore, it allows the use of solid materials as substrates for further biotransformation. SSF has gained attention in the last years being reported as a promising eco-technology that allows obtaining bioproducts of industrial interest using solid biomass (wastes and by-products). Main advantages over conventional submerged fermentation rely on the lower water and energy requirements, which generate minimum residual streams. However, drawbacks related to poor homogeneity and energy and mass transfer often appear, hindering the process yield and the downstream of the produced bioproducts. Despite the difficulties, many successful processes have been reported on the production of a variety of bioproducts such as hydrolytic enzymes, mostly carbohydrases for bioethanol production, and to a lesser extent, aromas, biosurfactants, biopesticides, bioplastics, organic acids or phenolic compounds. Most of the reported research focuses on process development at small scale; however, the main challenges to overcome in SSF are related to the upscaling and the development of a consistent and continuous operation. In this work, the main advances for the production of valuable/innovative bioproducts are presented and discussed.

Sustainability, 2018

Solid-state fermentation (SSF) is a promising technology for producing bioproducts from organic w... more Solid-state fermentation (SSF) is a promising technology for producing bioproducts from organic wastes. The objective of this study is to assess the feasibility of using digestate as substrate to produce hydrolytic enzymes, mainly cellulase and xylanase, by exploring three different inoculation strategies: (i) SSF with autochthonous microbiota; (ii) non-sterile SSF inoculated with Trichoderma reesei and (iii) sequential batch operation to select a specialized inoculum, testing two different residence times. Native microbial population did not show a significant cellulase production, suggesting the need for a specialized inoculum. The inoculation of Trichoderma reesei did not improve the enzymatic activity. On the other hand, inconsistent operation was achieved during sequential batch reactor in terms of specific oxygen uptake rate, temperature and enzymatic activity profile. Low cellulase and xylanase activities were attained and the main hypotheses are non-appropriate biomass selec...

Reviews in Environmental Science and Bio/Technology, 2019

Chemical processes and petroleum-based chemicals are being substituted by biological processes an... more Chemical processes and petroleum-based chemicals are being substituted by biological processes and bioproducts. Surfactants and biosurfactants are an example of this trend. Among the biosurfactants, sophorolipids (SLs) have excellent surface and interfacial tension properties, which make them ideal to be used in a wide variety of applications. SLs are produced at full scale through submerged fermentation of pure substrates (glucose and oleic acid). However, research trends suggest that there is a lot of interest to produce SLs from waste effluents and other low-cost substrates, both in submerged and solid-state fermentation processes. This study reviews the current research in the production of SLs via fermentation processes, focusing on those using wastes, by-products, or low-cost substrates (liquids or solids). It details the substrates, process variables, microorganisms, and use of supplementary media for batch, fed-batch, and continuous submerged or solid-state fermentation processes. Sophorolipids production based on industrial by-products and waste effluents presents huge potential for its application at an industrial scale in a more economical and environmentally friendly process, boosting the necessary change to circular economy.

Waste Management, 2019

This work studied the effect of mixing ratio (MR) and turning frequency (TF) in biowaste composti... more This work studied the effect of mixing ratio (MR) and turning frequency (TF) in biowaste composting (BW) with sugarcane filter cake (SFC) and star grass (SG), both on process performance (temperature, static respiration index, total organic carbon, total nitrogen and total phosphorus) and on product quality (pH, cation exchange capacity, electrical conductivity, organic matter, nutrients, stability, maturity, total coliforms and faecal coliforms), through the Principal Components Analysis (PCA). The Pearson correlation coefficients were calculated for all the quality parameters. A joint effect of mixing ratio and turning frequency was demonstrated, highlighting the importance of studying the operational parameters simultaneously. The results of the PCA showed that the best operating conditions and therefore higher product quality is achieved with a TF of twice a week and MR between 20 and 30% of SFC or SG. Additionally, it was found that a frequency of one turn per week generates the lowest product quality, regardless the co-substrate and the MR. The best treatment corresponded to BW composting with MR of 20% SFC and TF of two turnings per week. The obtained results allow to optimize the operation in composting facilities.

Journal of Cleaner Production, 2018

In this manuscript, we approach the production of biosurfactants as a cleaner alternative to the ... more In this manuscript, we approach the production of biosurfactants as a cleaner alternative to the chemically-produced surfactants currently used in a wide range of industries. Sophorolipids are microbially produced biosurfactants of the glycolipid type that have entered the market in select applications such as detergent or cosmetic formulation ingredients. This study focuses on sophorolipid production by the yeast Starmerella bombicola from stearic acid (C18:0), a low-cost carbon source that is difficult to work with in submerged fermentation since it remains a solid due to its high melting temperature. Consequently, optimizations of solidstate fermentation inoculated with Starmerella bombicola were studied for conversions of stearic acid and molasses to sophorolipids. Polyurethane foam functioned as the inert support. The effect of polyurethane foam density and water holding capacity was assessed and the process was optimized in terms of substrate and inoculum ratio. The best conditions were: foam with a density of 32 kg m-3 at 75% water holding capacity, 1.17:1 molasses/stearic acid (w/w) and 5% (v/w) inoculum, to obtain a yield of 0.211 g sophorolipids per g of substrates. Mass spectrometry revealed that the sophorolipids produced herein had high concentrations of diacetylated acidic and lactonic C18:0 forms. The results of interfacial properties studies revealed that C18:0 sophorolipids had promising surface tension lowering capacity and emulsification behavior. This study describes a new strategy to produce biosurfactants using low environmental impact technologies as an alternative to traditional ways to produce chemical detergents.