Producción de polihidroxialcanoatos a partir de suero lácteo y otras fuentes de carbono usando cultivos microbianos mixtos

Abstract

The consumerist human way of living has been linear and unsustainable since the XX century. This fact has led the Earth to a worrisome environmental imbalance. However, society is currently increasing its concern about this critical environmental situation and choosing for a more circular economy in order to mitigate the environmental impact. It is about breaking with the Produce – Consume – Discard chain. The circular economy proposes the reuse of “waste” as raw material for the development of new products. Together with a reduction in the consumerist behaviour of the human population, they can offer a partial solution to this environmental imbalance issue. However, society can do little if large organizations, either public or private, have no will to change. Large organizations have the greatest responsibility for the Earth’s environmental situation. However, they are the least interested in a more sustainable development, whether for lack of tools or for a purely economic aspect. This doctoral thesis aimed the integration of waste valorization processes on the production chain in order to implement a circular economy model in an important industry in Galicia as the dairy industry. Galicia is, by far, the Spanish region with the highest dairy production from bovine origin and, therefore, a great variety of dairy products. Therefore, cheese whey becomes a very abundant by-product in our community, but with a high polluting effect due to its high organic load. This pollutant condition must be counteracted. Fortunately, biotechnology allows the transformation of cheese whey into polyhydroxyalkanoates, a microbial derived polymer with very similar properties to those of some conventional plastics, but with biodegradable condition. During this doctoral thesis, the optimization of the polyhydroxyalkanoates production process was studied using cheese whey as substrate and mixed microbial cultures as inoculum. In parallel, a new experiment design was performed in order to integrate the production of bioalcohols and biopolymers. With this goal, a gaseous carbon source was valorised in a two-stage process, designed here for the first time.