Biorrefineria integral para la producción de aceite microbianoo a partir de residuos de la industria agroalimentaria

Resumen

1. Introduction Food waste (FW) generation results in an ethical and environmental problem. According to FAO, more than one third of the food produced globally is discarded or wasted [1]. FW is generated in a complicated process that comprises production chain and system, consumer participation, besides dietary habits [2]. FW may be defined as edible and non-edible food that are discarded at any step along the food chain: primary sector, manufacturing sector, logistics (food damaged during transportation), storage (expiry dates, loss of quality) and post-consumption [3, 4]. In the EU, households are estimated to produce the largest amount of FW, that is, 47 million tons, which represents 53% of total FW generation. The cost associated has been estimated to be around 143 billion € [5]. From an environmental point of view, at a global level, FW carbon footprint represents 3.6 Gt CO2-eq and, while in the EU, it reaches up to 1.86 Mt CO2-eq. Factors involved in FW carbon footprint depend on food life cycle and dietary habits Conversely, food waste may play an economic and social role, providing new job opportunities and allowing the development of new strategies that help the viability and diversity of rural and urban economies. FW recovery can help to reduce FW environmental impact, improving food safety and recycling energy nutrients. In this context, the biorefinery philosophy provides a similar strategy to that of petroleum-based refineries. However, biorefineries use biomass as raw-material and allow the incorporation of “corporate social responsibility” (CSR) and circular economy [6-9]. This doctoral thesis is focused on food waste recovery using the biorefinery concept and in a context of scientific and human interest, reflected by the large increase in studies related to food waste recovery. Firstly, this work deals with the chemical composition and statistical variability of FW from hospitality sector. Once this composition is analyzed, a work methodology is developed with the objective of producing quality biofuel, following the principles of the bioeconomy. In sum, specific objectives are the following: Specific objectives: 1. To study the composition of FW and analyze its role in biorefineries. 2. To characterize FW from hospitality sector and its subsequent utilization as a raw material for a biorefinery. 3. To characterize triglyceride content and fatty acid composition of solid food waste , followed by its transesterification and further biodiesel characterization, according to standard EN 14214. 4. To optimize the oil extracted from SFW by response surface modeling, using ultrasound as energy. 5. To produce biodiesel from oleaginous yeast Rhodosporidium touruloides Y-27012, using FW from hospitality sector as raw material. 2. Contents of research Once the initial question which motivates the development of this thesis has been introduced, together with the objectives, the next step is to address, as in all research work, a literature review to evaluate the state of the art concerning the processes of food waste recovery. This is done in chapter 2, with special emphasis on food waste management from a point of view of FW nutrients, their derivates and interactions, which are of great importance for new strategies in biorefinery processes. Since the work proposed for this thesis has a mainly empirical character, once the importance of nutrients in the recovery of waste has been established, a scale study of the hospitality sector is carried out. To assess potential biorefinery development, food waste composition derived from local catering services is studied. Moisture, lipids, starch, proteins, metal profile and trace element content are analyzed in chapter 3. Furthermore, a statistical variability test, in combination with a principal component analysis, allow both the establishment of specific variations in waste composition and relationship with waste typology, i.e. meat and protein variation. Combination of both chemical characterization and statistical study provides a good decision-making tool for further FW processing and valorization. Based on results presented in chapter 3, two different processes are developed. Process one: extracted oil from food waste is used as raw material to produce biodiesel (chapter 4). Process two: other nutrients, i.e. starch, protein and fiber are used to produce microbial oil and biodiesel (chapter 5). Process described in chapter 4 is carried out in two steps; firstly, the feasibility of the use of oil, extracted from SFW from different establishments, to produce biodiesel that meets European standard EN14214 is studied. Fatty acid composition is analyzed and potential differences concerning the source are evaluated through principal component analysis. Also, oil properties, namely water content and acid value are evaluated to analyze whether an esterification pretreatment is needed. Finally, several SFW biodiesel chemical and physical properties are analyzed. Secondly, improving pre-treatment and treatment for SFW biodiesel production is studied. Due to high free fatty acid content, acid esterification pre-treatment is conducted, followed by a basic transesterification optimization. Reaction time is improved by assisting transesterification with ultrasound (US). Response surface methodology is selected to perform the experimental design. Finally, chapter 5 focuses on the valorization of residues from food service sector to produce biodiesel through fermentation, using oleaginous yeasts, which accumulate intracellularly lipids. In light of the starch and protein content of FW, controlled enzymatic hydrolysis is considered as a feasible alternative, and required enzymes are provided through solid state fermentation using A. awamori and potato peel as substrate. As result of the combination of SSF enzymes and further hydrolysis, a fermentation medium rich in carbon and nitrogen that allows microbial growth and lipid accumulation is found. Yeast Rhodosporidium turuloides is selected to provide microbial oil, with subsequent biodiesel production that meets European standard EN14214. 3.Conclusions The Food waste (FW) typology analysis showed an elevated presence of rich-in-starch foodstuff. The chemical quantitative analysis showed a high concentration of lipids, starch and protein and presented a profile with a high degradation potential, which can be used for direct and indirect valorization through biorefinery processes. Statistical analysis helps to understand the complex matrix of FW and shows the importance of developing a specific analysis. The lipid fraction extracted from Solid Food Waste (SFW) from different restaurants showed some significant differences in fatty acid composition. However, this composition was similar to that of vegetable oils. In spite of these differences, physical and chemical properties were similar between oils, with the exception of acid value. Consequently, it seems possible to work with mixtures of oils extracted from SFW from different restaurants to produce biodiesel. Thus, as these oils show a strong tendency to present a high content of free fatty acids, a preliminary acid value analysis and a further acid catalyzed-esterification pre-treatment are needed. Compared with conventional methods, a US-assisted reaction provided significant advantages in reaction time and energy savings. Physical and chemical property analysis showed that biodiesel fulfils European biodiesel standards, except regarding oxidation stability, FAME yield and glyceride content. For this reason, this biofuel can be used as fuel by blending it with diesel fuel or by adding phenolic antioxidants. Finally, the results show that a sustainable biorefinery, based on the valorization of food-industry wastes using Rhodosporidium toruloides Y-27012, for the production of microbial oil (MO) that is transesterified into biodiesel, is feasible and is in accordance with the international standard normative. The suitability of food waste to produce an alternative culture medium for MO production in two steps (solid state fermentation and hydrolysis) has been demonstrated. A. awamori presented a perfect crude enzyme consortium, able to degrade starch and protein into adequate nutrients for Rhodosporidium toruloides Y-27012 fermentation.t The MO profile presented a similar fatty acid profile to that of other raw materials, such as poppy-seeds, solid food waste oil or Cryptococcus curvatus. The biodiesel showed properties within the limits described by the European normative. 4. References [1] Jenny Gustavsson CC, Ulf Sonesson and Andreas Emanuelsson. global losses and food waste-Extent, causes and prevention. By SIK - The Swedish Institute for Food and Biotechnology 2013. [2] Priefer C, Jörissen J, Bräutigam K-R. Technology options for feeding 10 billion people. Options for cutting food waste. Study for the European Parliament. Report no. IP/A/STOA/FWC/2008-096/Lot7/C1/SC2 -SC4. Science and Technology Options 2013. [3] Carmona-Cabello M, Garcia IL, Leiva-Candia D, Dorado MP. Valorization of food waste based on its composition through the concept of biorefinery. Current Opinion in Green and Sustainable Chemistry 2018;14:67-79. [4] Kearney J. Food consumption trends and drivers. Philosophical transactions of the Royal Society of London Series B, Biological sciences 2010;365(1554):2793-807. [5] Stenmarck A, Jensen C, Quested T, Moates G. Estimates of European food waste levels. European Union; 2016. [6] Dahiya S, Kumar AN, Shanthi Sravan J, Chatterjee S, Sarkar O, Mohan SV. Food waste biorefinery: Sustainable strategy for circular bioeconomy. Bioresource Technology 2018;248:2-12. [7] Du C, Lin SKC, Koutinas A, Wang R, Dorado P, Webb C. A wheat biorefining strategy based on solid-state fermentation for fermentative production of succinic acid. Bioresource Technology 2008;99(17):8310-5. [8] Hassan SS, Williams GA, Jaiswal AK. Lignocellulosic Biorefineries in Europe: Current State and Prospects. Trends in Biotechnology 2019;37(3):231-4. [9] Teigiserova DA, Hamelin L, Thomsen M. Review of high-value food waste and food residues biorefineries with focus on unavoidable wastes from processing. Resources, Conservation and Recycling 2019;149:413-26.