Strategies for Automated Control of the Bioproduction of Mcl-PHA Biopolymers

Medium-chain-length polyhydroxyalkanoates (mcl-PHAs) are polyesters synthesized by numerous bacteria as storage material. Despite being promising candidates for biodegradable materials of industrial interest and environmental value, their usage is still rather limited because of high production costs. One of the areas with considerable potential for further improvements is control of the production process. This paper deals with the experimental work related to the design of control strategies for mcl-PHA biopolymer production process (Pseudomonas putida KT2442 fed-batch cultivations). For this bioprocess, a set of five control strategies (two main and three auxiliary strategies) have been proposed, together with the proper sequence of their switching during the fedbatch part of the production process. The application of these strategies with octanoic acid as a sole carbon source resulted in intracellular PHA content (max. mass fraction 65% of mcl-PHA in cell dry mass (g [g.sup.-1]) and PHA productivity (max. 0.89 g [L.sup.-1] [h.sup.-1]) comparable to the best results reported in the literature for this type of strain and carbon substrate.Key words: fermentation, process control, biopolymer production, fed-batch cultivation