Bio-Based organic and hydroxy acid production with corynebacterium glutamicum

Organic acids are used in several industrial sectors, such as food or pharmaceutical industry and serve as building block chemicals for a vast variety of products. Up to date many of them are obtained from petrochemical resources, implementing energy intensive chemical refining and waste production with a high environmental impact [1]. The enormous annual demand requests the development of efficient and sustainable bioprocesses for organic acid production. Recent studies explored the potential of Corynebacterium glutamicum for the production of several organic acids and demonstrated different strategies to improve its performance. In the last decade, also the production of hydroxy and polyhydroxy acids with C. glutamicum attracted attention. Especially, because of the high economic value of polyhydroxy acids, this field receives extensive research attention. Being biodegradable and biocompatible, they are an attractive alternative to classical petrochemical-derived plastics. The advantage in producing such substances with C. glutamicum is the use of simple media, free of complex components, in contrast to e.g. recombinant yeast. This cheapens the overall fermentation process, and simplifies in addition the product purification, resulting in lower waste production. Furthermore, the production of foodrelated compounds, or cosmetics and chemicals directly applied to humans, is not as critical with C. glutamicum, while with Gram-negative bacteria, the production is accompanied by contamination with pyrogenic compounds (endotoxins). This chapter summarizes the current knowledge and recent achievements on metabolic and process engineering approaches to tailor C. glutamicum with the focus on bio-based production of succinate, the alpha hydroxy acids L-lactate, D-lactate, and glycolate, as well as the biodegradeable polyester polyhydroxybutyrate.