[en] Cheese Wey is the by-product of the cheese industry, due to its composition of lactose (up to 85%), it is an interesting and promising alternative to be used as a substrate to produce polihidroxialkanoatos (PHA). More than 50% of whey produced in cheese production is not effectively treated as a major environmental problem because of the amount of undegraded organic matter that contaminates rivers, lakes, seas, etc. The treatments of valorization of cheese whey aim at maximum recovery of the raw material turning this byproducts into substrates useful for other industrial purposes and among which we can count the production of PHA. Since the last decades, there has been considerable interest in the development of new technologies in the production of bioplastics as a replacement for conventional plastics due to the problems generated by the accumulation and the almost no elimination in the environment. Polyhydroxyalkanoates (PHA) have attracted considerable attention in recent times due to the fact that industrial waste is used to obtain it, which alleviates the organic load that is otherwise disposed of in landfills; And because it is presented as a viable alternative to petrochemical plastics. PHAs are a type of biopolymers produced by microbial synthesis which are used as energy reserves for their metabolic processes. Current methods for the production of PHA on an industrial scale are mostly based on pure microbial cultures requiring complex and costly processing procedures. But currently there are alternatives based on mixed microbial cultures that seeks to reduce production costs, because it does not require sterilization processes and use bacteria that can adapt well to substrates of diverse origin as waste materials from agro-industry and dairy. The alternative approach to producing PHA using mixed microbial culture still requires further study and optimization in the process to obtain a Higher cellular PHA content and productivity in addition to improving current processes using pure microbial cultures. This thesis proposes a process to obtain PHA in three phases (acidogenic fermentation, selection and enrichment of accumulating microorganisms and production of PHA) at laboratory scale, using mixed microbial cultures and Dairy serum as the initial substrate of the process It is intended to study the fatty acid profile obtained as a consequence of the change in parameters in anaerobic fermentation processes, such as reactor type, solids retention time (SRT), pH, organic loading rate (OLR) , In order to reach the highest concentration of volatile fatty acids (VFA), which will later be used in a selection process of microorganisms in a second aerobic phase (SBR) and finally to evaluate the productivity and production of PHA obtained in a discontinuous reactor (Fed-Bacht). It is also expected to evaluate the effect of anaerobic fermentation on PHA properties obtained as final product. In the first chapter, a bibliographical review of the studies carried out until the present time on the obtaining of PHA and the use of the milk substrate is made for this purpose. The second chapter consist in the materials and methods related with the development of this thesis. The third chapter studies two types of reactors for the fermentation process of whey to obtain volatile fatty acids. A UASB (continuous reactor) reactor and another SBR (discontinuous reactor) were used to vary the organic loading rates Differences between the two reactors at their maximum acidification and acid profile obtained in each reactor. The fourth chapter, studies the effect of the reactor's operational parameters on pH, solid retention time (TRS), organic loading rate in an A-SBR reactor to study them, as well as observing how these variables modify the Profile of acids obtained and the degree of acidification of the milk substrate. The fifth chapter, studies the variation of the acid profile obtained in the acidogenic fermentation pro changes in the organic loading rate and the effect on the characteristics of the PHA obtained in the distribution of formed P-PHB (PHB / PHV). Finally, a final section highlights the most important conclusions of this work. General objective: The production of PHA through mixed microbial cultures using cheese whey as substrate, in a three-step process: acidogenesis, enrichment of microbial culture and production of PHA. Specific objective: The study of the operational variables in the acidogenic reactor such as pH, reactor type, OLR and SRT in the production and profile of volatile fatty acids obtained and how it affects the production of PHA in its composition.

[gl] O soro é un subproduto xerado na industria de queixo. Normalmente a graxa está separada da graxa e, en moitas industrias, a proteína é un soro cuxa composición é principalmente lactosa (ata o 85%). Máis que o 50% do soro de leite producido na produción de queixo non é adecuadamente tratada, que é un problema grave, debido á gran cantidade de material orgánico sen degradar final contaminar o medio ambiente. A recuperación do soro de leite ten como obxectivo recuperar os subprodutos que teñen un gran valor no mercado. Unha alternativa interesante e prometedora para o seu uso como substrato para a produción de polihidroxialcanoatos (PHA). Nas últimas décadas, apareceu un gran interese no desenvolvemento de novas tecnoloxías para a obtención de bioplásticos que poden substituír os plásticos convencionais. Estes xeran problemas no medio debido á súa acumulación e á súa baixa biodegradación. Poliidroxialcanoatos atraeron considerable atención recentemente, xa que pode ser obtido a partir de residuos industriais, ademais dalgúns plásticos teñen propiedades similares de orixe petroquímica. As PHA producen biopolímeros sintetizados polo microorganismo como reserva de enerxía para poder realizar procesos metabólicos. Na actualidade, úsanse tecnoloxías de cultivos puros para a produción de PHA a escala industrial, que requiren procesos de produción complexos e custosos. Actualmente novas alternativas foron desenvolvidas con base no uso de cultivos microbianas mixtas para reducir os custos de produción, porque non esixen aos seus procesos de esterilización de produción. O proceso de obtención de PHA desde a cultura microbiana mixta aínda require un estudo máis profundo e optimización, a fin de obter unha acumulación de PHA en microorganismos e tamén para obter unha maior produtividade e produtividade máis para mellorar os procesos existentes mediante cultivos puras microbianas. Esta tese propón un proceso para a obtención de PHA en tres fases a escala de laboratorio, utilizando cultivos microbianos mixtos e soro de leite como fonte de sustrato. Na primeira fase farase a fermentación acidógena para a produción de ácidos graxos volátiles. Nunha segunda fase, a selección de microorganismos realízase con capacidade de acumulación de PHA e finalmente na terceira fase, a capacidade máxima de acumulación dos microorganismos de PHA determínase. No primeiro capítulo dunha revisión da literatura de estudos realizados ata agora na obtención de PHA eo uso de soro de leite como materia prima está feito. O segundo capítulo, os materiais e métodos utilizados na realización das experiencias descritas. A fermentación terceiro capítulo, soro de leite é estudada por ácidos graxos volátiles, utilizando dous tipos de reactores de reactor de desaugue ascendente leito de lodo do reactor (UASB) e unha secuencia discontinua (SBR). variando cargas orgánicas diferencia entre os dous reactores en acidificación e perfil de ácidos obtidos en cada reactor máximo. O cuarto capítulo é estudado nun reactor SBR a influencia do pH, tempo de retención de sólidos (TRS), e da carga orgánica na distribución obtida de ácidos graxos volátiles eo grao de acidificación. No quinto capítulo, o perfil de variación de ácidos obtidos no copolímero distribución fermentación acidogenica de P (PHB / PHV) na fase de acumulación de PHA foi estudada. Finalmente, nunha última sección as principais conclusións deste traballo se destaca. Obxectivo: O estudo da produción de PHA culturas microbianas mixtas utilizando como substrato de soro de leite, utilizando un proceso de tres pasos: fermentación acidogenica de cultura mixta de PHA ea produción microbiana de enriquecemento do soro de leite. Obxectivo específico: variables operativas analizados no reactor acidogenica tales como o pH, o tipo de reactor, e TRS VCO perfil de produción obtidos e ácidos graxos volátiles e como se afecta a produción de PHA na composición.