Elia Tomas-Pejo

• Researcher at Madrid Institute for Advanced Studies

Environmental concerns are rising the need to find cost-effective alternatives to fossil oils. In this sense, short-chain fatty acids (SCFAs) are proposed as carbon source for microbial oils production that can be converted into oleochemicals. This investigation took advantage of the outstanding traits of recombinant Yarrowia lipolytica strains to...

Bioethanol is the most commonly used biofuel. It is an alternative to replace fossil fuels in renewable energy; it can be produced from lignocellulosic feedstock using a biotechnological process. The participation of microorganisms is crucial in the bioconversion process of fermentation for ethanol production and can involve bacteria, fungi, and ye...

Converting waste into high-value products promotes sustainability by reducing waste and creating new revenue streams. This study investigates the potential of diverse yeasts for microbial oil production by utilizing short-chain fatty acids (SCFAs) that can be produced from organic waste and focuses on identifying strains with the best SCFA utilisat...

Background Short-chain fatty acids (SCFAs) are cost-effective carbon sources for an affordable production of lipids. Hexanoic acid, the acid with the longest carbon chain in the SCFAs pool, is produced in anaerobic fermentation of organic residues and its use is very challenging, even inhibiting oleaginous yeasts growth. Results In this investigat...

Cutaneotrichosporon curvatum and Yarrowia lipolytica can accumulate microbial oils using short-chain fatty acids (SCFA) as carbon sources. SCFAs-rich media often contain significant amounts of nitrogen that prevent high carbon:nitrogen (C:N) ratios necessary to boost lipid production. This work assessed the intrinsic ability of C. curvatum and Y. l...

Global reliance on fossil oil should shift to cleaner alternatives to get a decarbonized society. One option to achieve this ambitious goal is the use of biochemicals produced from lignocellulosic biomass (LCB). The inherent low biodegradability of LCB and the inhibitory compounds that might be released during pretreatment are two main challenges f...

Carboxylic acids have become interesting platform molecules in the last years due to their versatility to act as carbon sources for different microorganisms or as precursors for the chemical industry. Among carboxylic acids, short-chain fatty acids (SCFAs) such as acetic, propionic, butyric, valeric, and caproic acids can be biotechnologically prod...

Microbial lipids for chemical synthesis are commonly obtained from sugar‐based substrates which in most cases is not economically viable. As a low‐cost carbon source, short‐chain fatty acids (SCFAs) that can be obtained from food wastes offer an interesting alternative for achieving an affordable lipid production process. In this study, SCFAs were...

This study assessed a strategy for food waste (FW) valorization into multiple products by applying a cascade combination of only two anaerobic processes using open mixed cultures. FWs were firstly subjected to an anaerobic fermentation (AF) to generate an effluent rich in valuable bioproducts. The remaining solid fraction of AF effluent was further...

Background Microbial lipids are found to be an interesting green alternative to expand available oil sources for the chemical industry. Yeasts are considered a promising platform for sustainable lipid production. Remarkably, some oleaginous yeasts have even shown the ability to grow and accumulate lipids using unusual carbon sources derived from or...

This investigation evaluated the effect of process pH in the metabolite spectrum generated during the anaerobic fermentation (AF) of three carbohydrate-rich wastes (residual cucumber, tomato, and lettuce). For such a purpose, two groups of AF reactors were operated in parallel. One group was operated under inherent conditions of pH upon degradation...

Dry anaerobic digestion (D-AD) generates nitrogen-rich effluents that are normally neglected in the circular bioeconomy. The high turbidity and ammonium content hamper nitrogen recovery from these effluents via biological processes, such as microalgae culture. The goal of this study was to demonstrate microalgae growth viability in high-strength D-...

Increasing yeast robustness against lignocellulosic-derived inhibitors and insoluble solids in bioethanol production is essential for the transition to a bio-based economy. This work evaluates the effect exerted by insoluble solids on yeast tolerance to inhibitory compounds, which is crucial in high gravity processes. Adaptive laboratory evolution...

Carboxylic acids, traditionally produced from fossil fuels, might be generated from renewable biomass resources via anaerobic fermentation. Considering that the microbial activity of this bioprocess is ruled by the imposed hydraulic retention time (HRT), this investigation explored the relationship between process stability and microbial community....

To properly exploit short-chain fatty acids (SCFAs) in the chemical industry, it is of foremost importance to ensure stable SCFA profile production via anaerobic fermentation (AF). The different macromolecular distribution of food wastes (FWs) used as feedstock might be crucial for process outcome. Targeting at a specific SCFAs profile and yield, t...

Unspecific microorganisms consortia are normally used in anaerobic biodegradation of solid wastes. However, these consortia can be tuned to optimally obtain determined bioproducts. In this study, high value-added products and biogas were obtained via an innovative two-stage anaerobic bioprocess from microalgae biomass. The anaerobic fermentation (A...

The organic fraction of municipal waste (OFMW), source-sorted (SS-OFMW) and non-sorted (NS-OFMW), was used as raw material for the sequential production of bioethanol and biogas. Non-isothermal and simultaneous saccharification and fermentation (NSSF) resulted in maximum ethanol concentrations of 51 g/L and 26 g/L for SS-OFMW and NS-OFMW samples, s...

Volatile fatty acids (VFAs) are platform molecules with numerous applications. They can be obtained by adjusting the operational conditions of anaerobic digestion to avoid methanogenesis while focusing on fermentative stages. There are gaps in the knowledge of how, from a life-cycle perspective, the fermentative process performs in VFAs production...

The present study describes the isolation of the novel strain Candida intermedia CBS 141442 and investigates the potential of this microorganism for the conversion of lignocellulosic streams. Different C. intermedia clones were isolated during an adaptive laboratory evolution experiment under the selection pressure of lignocellulosic hydrolysate an...

This study assessed the feasibility of melon and watermelon residues for the co-production of short-chain fatty acids (SCFAs) and hydrogen (H2) via single-stage anaerobic fermentation. The high content of carbohydrates and readily biodegradable organic matter in the wastes, along with the acid pH (5.6–5.8) imposed in the reactors, were key factors...

Short-chain fatty acids (SCFAs) are considered building blocks for bioproducts in the so-called carboxylate platform. These compounds can be sustainably produced via anaerobic fermentation (AF) of organic substrates, such as microalgae. However, SCFAs bioconversion efficiency is hampered by the hard cell wall of some microalgae. In this study, one...

Using residual material instead of sugars as substrate for oleaginous microorganisms is a promising approach that may reduce the production costs of microbial lipid. In this study, five oleaginous yeasts were screened for their ability to grow and produce lipid utilizing volatile fatty acids (VFAs), generated from anaerobic fermentation of microalg...

Cellulose valorisation has been successfully addressed for years. However, the use of hemicellulosic hydrolysates is limited due to the presence of C5-sugars and inhibitors formed during pretreatment. Bacillus coagulans is one of the few bacteria able to utilize both C6- and C5-sugars to produce L-lactic acid, but its susceptibility to the lignocel...

This study assessed the potential of using microalgae anaerobic fermentation as a novel choice for producing microbial oils and biogas. Microalgae biomass (Chlorella vulgaris) was used for volatile fatty acids (VFAs) production at three organic loading rates (OLR = 6, 9, 12 g COD/Ld). Regardless of the OLR, anaerobic systems displayed similar organ...

The expansion of urban green areas has boosted the accumulation of gardening lignocellulosic residues that could be potentially used to produce platform chemicals like lactic acid. However, when using lignocelluloses, pretreatment step, such as steam explosion, is often needed to favour sugar release. Considering that the conversion of glucose from...

A wide range of biofuels and bio-based products can be produced from lignocellulose considering its high compositional diversity. Ethanol production by yeasts from cellulosic glucose is well-known, while hemicellulosic xylose utilization is still challenging. This work proposes the use the xylose for l-lactic acid fermentation. In this context, a s...

Disturbances in anaerobic digestion (AD) negatively impact the overall reactor performance. These adverse effects have been widely investigated for methane generation. However, AD recently appeared as a potential technology to obtain volatile fatty acids (VFAs) and thus, the impact of process disturbances must be evaluated. In this sense, microbial...

The application of enzymes offers an enormous potential in the improvement of existing industrial procedures and in the establishment of new processes for obtaining high‐added value products. Enzymes provide cleaner and more efficient industrial processes and contribute to the sustainability concept. In this sense, laccases are very versatile bioca...

This study evaluated the feasibility of the anaerobic digestion as a sustainable valorisation strategy for volatile fatty acids production from agroindustrial waste (cucumber, tomato and lettuce). High bioconversion efficiencies were reached by operating the reactors at 25 °C, 3 g VS·d-1·L-1 with pH adjustment. Cucumber fermentation achieved the hi...

Microbial oils are proposed as a suitable alternative to petroleum‐based chemistry in terms of environmental preservation. These oils have traditionally been studied using sugar‐based feedstock, which implies high costs, substrate limitation, and high contamination risks. In this sense, low‐cost carbon sources such as volatile fatty acids (VFAs) ar...

The application of enzymes offers an enormous potential in the improvement of existing industrial procedures and in the establishment of new processes for obtaining high‐added value products. Enzymes provide cleaner and more efficient industrial processes and contribute to the sustainability concept. In this sense, laccases are very versatile bioca...

This investigation compared the digestion in completely stirred tank reactor (CSTR) of Spirulina platensis at two digestion temperatures (25 and 35 °C). This comparison was conducted in terms methane production, organic matter (COD) removal, volatile fatty acids (VFAs) production and nitrogen mineralization. In mesophilic range, 42%tCOD removal and...

Abstract Lignocellulosic ethanol production requires high substrate concentrations for its cost-competitiveness. This implies the presence of high concentrations of insoluble solids (IS) at the initial stages of the process, which may limit the fermentation performance of the corresponding microorganism. The presence of 40–60% IS (w/w) resulted in...

Since xylose is the second most abundant sugar in lignocellulose, using microorganisms able to metabolize it into bio-based chemicals like lactic acid is an attractive approach. In this study, Lactobacillus pentosus CECT4023T was evolved to improve its xylose fermentation capacity even at acid pH by adaptive laboratory evolution in repeated anaerob...

BACKGROUND Anaerobic digestion (AD) could be designed as a source of volatile fatty acids (VFAs). However, acidogenesis optimization for novel substrates such as Chlorella vulgaris biomass needs to be investigated considering parameters such as temperature (T), organic loading rate (OLR), hydraulic retention time (HRT) and the adaptation of the slu...

Lactic acid is a versatile chemical that can be produced via fermentation of lignocellulosic materials. The heterolactic strain Lactobacillus pentosus CECT 4023 T, that can consume glucose and xylose, was studied to produce lactic acid from steam exploded wheat straw prehydrolysate. The effect of temperature and pH on bacterial growth was analyzed....

Volatile fatty acids (VFAs) produced via anaerobic digestion (AD) are regarded as a low cost production process of building blocks of interest for the chemical industry. In this study, VFAs and methane production were assessed in batch reactors at different temperature ranges (psychrophilic 25°C, mesophilic 35°C, thermophilic 50°C) and different pH...

During the last decade, a lot of research has been focused on identifying the methane yields achievable when using microalgae biomass (fresh and pretreated) as a substrate in anaerobic digestion. Encountered differences are frequently attributed to the different microalgae strains (cell walls and macromolecular profiles) or the different metabolic...

The production of high added-value products from lignocellulose is proposed as a suitable alternative to petroleum-based resources in terms of environmental preservation, sustainability, and circular economy. Lactic acid is a versatile building block that can be produced via fermentative routes by several groups of microorganisms, including yeasts...

The potential of co-producing two different biofuels from a lignocellulosic substrate (wheat straw), according to a biorefinery concept, has been investigated. For such a purpose, simultaneous saccharification and fermentation (SSF) from the hemicellulosic and cellulosic fractions was performed for maximizing bioethanol production. The non-washed w...

Ethanol fuel is leading the transition towards a post-petrol era in the transport sector worldwide. Ethanol is produced via sugar fermentation processes by yeasts or bacteria. Although the current industrial production of ethanol mainly involves the use of starch- and sugar-based feedstocks, lignocellulosic biomass is expected to play a key role as...

As a result of the increasing population and industrial development, there is an enormous energy demand worldwide. For this reason, the research on the potential of microalgae (including also cyanobacteria) as a third-generation feedstock for bioenergy production has markedly increased. Besides biofuels (biogas, bioethanol, biodiesel, etc.), algae...

The continuous increase in the world energy and chemicals demand requires the development of sustainable alternatives to non-renewable sources of energy. Biomass facilities and biorefineries represent interesting options to gradually replace the present industry based on fossil fuels. Lignocellulose is the most promising feedstock to be used in bio...

En la conversión de los materiales lignocelulósicos a etanol por métodos biotecnológicos se requieren altas cargas de sustrato para alcanzar concentraciones de producto superiores a 40 g/L, y garantizar de ese modo la rentabilidad del proceso. Sin embargo, las severas condiciones (altas temperaturas, altas presiones, etc.) a las que se somete la bi...

The addition of laccase enzymes reduces the amount of phenols present in lignocellulosic pretreated materials and increases their fermentability. However, laccase addition in combination with cellulases reduces hydrolysis yields. In this work, hybrid hydrolysis and fermentation (HHF) configuration allowed overcoming the negative effect of laccase t...

Background: Laccases represent a very powerful tool to improve biorefining processes from lignocellulosic feedstocks. These enzymes are being investigated not only for potential use as pretreatment agents in bioethanol production, mainly as a delignifying agent, but also as a biotechnological tool for removal of inhibitors (mainly phenols) of subse...

Anaerobic digestion of microalgae is hampered by its complex cell wall. Against this background, cyanobacteria cell walls render this biomass as an ideal substrate for overcoming this drawback. The aim of the present study was to compare the growth of two cyanobacteria (Aphanizomenon ovalisporum and Anabaena planctonica) and a microalga (Chlorella...

When laccases are applied for detoxifying steam-exploded slurries, enzymatic hydrolysis is affected. In this study, 10% (w/v) of dry weight (DW) slurry or water insoluble solid fraction were subjected to 48 h enzymatic hydrolysis in the presence of different laccase loadings (0.1, 0.5, 5 or 10 IU/g DW). All laccase dosages higher than 0.1 IU/g DW s...

Background: Inhibitors that are generated during thermochemical pretreatment and hydrolysis impair the performance of microorganisms during fermentation of lignocellulosic hydrolysates. In omitting costly detoxification steps, the fermentation process relies extensively on the performance of the fermenting microorganism. One attractive option of i...

Phenols are known as inhibitors for cellulases and fermentative microorganisms in bioethanol production processes. The addition of laccases removes the phenolic compounds and subsequently reduces the lag phase of the fermentative microorganism. However, the application of laccases diminishes glucose release during the enzymatic hydrolysis. In this...

Future biorefineries will integrate biomass conversion processes to produce fuels, power, heat and value-added chemicals. Due to its low price and wide distribution, lignocellulosic biomass is expected to play an important role toward this goal. Regarding renewable biofuel production, bioethanol from lignocellulosic feedstocks is considered the mos...

When employing biotechnological processes for the procurement of biofuels and bio-products from microalgae, one of the most critical steps affecting economy and yields is the “cell disruption” stage. Currently, enzymatic cell disruption has delivered effective and cost competitive results when compared to mechanical and chemical cell disruption met...

BACKGROUND The hard cell wall of some microalgae hampers an efficient methane production when using those substrates. The present study investigated the effect of two groups of biocatalysts, namely carbohydrases and proteases, applied to Chlorella vulgaris and Scenedesmus sp. for microalgae hydrolysis prior anaerobic digestion.RESULTSC. vulgaris su...

Development of xylose-fermenting yeast strains that are tolerant to the inhibitors present in lignocellulosic hydrolysates is crucial to achieve efficient bioethanol production processes. In this study, the importance of the propagation strategy for obtaining robust cells was studied. Addition of hydrolysate during propagation of the cells adapted...

The presence of inhibitors compounds after pretreatment of lignocellulosic materials affects the saccharification and fermentation steps in bioethanol production processes. Even though, external addition of laccases selectively removes the phenolic compounds from lignocellulosic prehydrolysates, when it is coupled to saccharification step, lower hy...

There have been intense efforts in the scientific community and industry to engineer S. cerevisiae strains to co-consume xylose and glucose. In this context, this paper describes a process for introducing a barcode into an industrial xylose fermenting yeast strains to ensure quick and reliable identification of patented industrial strains. Furtherm...

Lignocellulosic bioethanol is expected to play an important role in fossil fuel replacement in the short term. Process integration, improvements in water economy, and increased ethanol titers are key considerations for cost-effective large-scale production. The use of whole steam-pretreated slurries under high dry matter (DM) conditions and convers...

In brewing and ethanol-based biofuel industries, high-gravity fermentation produces 10-15% (v/v) ethanol, resulting in improved overall productivity, reduced capital cost, and reduced energy input compared to processing at normal gravity. High-gravity technology ensures a successful implementation of cellulose to ethanol conversion as a cost-compet...

The expansion of established cereal-based plants by integrating second generation ethanol production into their current operations might be the best first step to successful commercialization of cellulosic ethanol. Joining first and second generation facilities could allow costs reduction for new technology implementation. The media supplementation...

Ethanol production from lignocellulosic raw materials includes a pretreatment step before enzymatic hydrolysis (EH). Pretreated substrates contain complex hemicelluloses in the solid fraction that can protect the cellulose from enzymatic attack. In addition, soluble xylooligomers are contained in the pretreated materials and may have an inhibitory...

The high demand for energy worldwide, coupled with the depletion of the world's petroleum supply and the concern about global climate change have resulted in a resurgence in the development of alternative fuels. Nowadays, bioethanol is one of the most important renewable fuels contributing to the mitigation of the negative environmental impacts gen...

This chapter focuses on pretreatment technologies for lignocellulose-to-Bioethanol conversion. The selection of an appropriate pretreatment determines the process configuration requirements for hydrolysis and fermentation as each step has a large impact on all subsequent stages. The chemistry of the pretreatment has a remarkable importance due to i...

An efficient fermenting microorganism for bioethanol production from lignocellulose is highly tolerant to the inhibitors released during pretreatment and is able to ferment efficiently both glucose and xylose. In this study, directed evolution was employed to improve the xylose fermenting Saccharomyces cerevisiae F12 strain for bioethanol productio...

Biofuel produced from lignocellulosic materials, so-called second generation bioethanol shows energetic, economic and environmental advantages in comparison to bioethanol from starch or sugar. However, physical and chemical barriers caused by the close association of the main components of lignocellulosic biomass, hinder the hydrolysis of cellulose...

Solid content in the simultaneous saccharification and fermentation (SSF) broth should be as high as possible in order to reach higher ethanol concentration. In this work, several feeding strategies for ethanol production from steam-exploded wheat straw by Kluyveromyces marxianus CECT 10875 have been studied with the aim of obtaining higher ethanol...

This paper reviews current status of bioethanol production including substrates, fermenting microorganisms and technology for a full-scale process development. Considering main drawbacks, several parameters (high substrate loadings, sugar recovery after pretreatment, tolerance to inhibitory compounds and xylose fermentation by yeast) must be optimi...

This study was aimed to study the effect of commercial cellulases (Celluclast 1.5 LFG) on Kluyveromyces marxianus CECT 10875 growth and ethanol production in SSF processes. Preliminary tests carried out in glucose (50 g/L) fermentation medium showed that high enzyme amounts (2.5-3.5 FPU/mL) could cause a negative effect on K. marxianus growth rate...

In this study, bioethanol production from steam-exploded wheat straw using different process configurations was evaluated using two Saccharomyces cerevisiae strains, F12 and Red Star. The strain F12 has been engineerically modified to allow xylose consumption as cereal straw contain considerable amounts of pentoses. Red Star is a robust hexose-ferm...

La presente Tesis Doctoral aborda el hecho de la integración de las etapas de proceso mediante el estudio de diferentes configuraciones para la producción de etanol a partir de paja de trigo. La producción máxima de etanol, así como los rendimientos y las productividades volumétricas han sido comparadas empleando diferentes estrategias de hidrólisi...