Biosynthesized intracellularly by various microorganisms, PHAs are potential replacements for conventional plastics. Cacao mucilage exudate (CME) is a liquid by-product of cacao bean fermentation. CME was used as a substrate for polyhydroxyalkanoates (PHAs) production. Previous studies showed that the Carbon:Nitrogen (C:N) ratio is the nutritional variable that most influence PHA production when using culture media containing liquid cacao residues. This study follows the process of a native microorganism (Bacillus megaterium B2) adaptation to CME-based media with various C:N ratios. The goal of the adaptation is to increase PHA yield and productivity. The CME-based medium with a C:N ratio of 12.5 enabled a maximum product yield of 0.89 g/g and a productivity of 0.19 g/L*h for PHA. An experimental design allowed the derivation of a mathematical function correlating the product yield to the C:N ratio. Function optimization suggested a maximum product yield at a C:N ratio of 12.4, obtaining an increase of 6% in this value and a productivity of 2 g/L*h. On the other hand, chlorinated solvents are typically used to isolate and purify PHAs from biomass. We tested alternative extraction methods to substitute the traditional solvents. Using Chemical agents (SDS, NaClO, H2O2 and C2H5OH) and mechanical disruption (ultrasound) we isolated PHA with 99% compared to the traditional method.

Effect of the C:N ratio in PHA yield and productivity by a native microorganism using culture media containing liquid cacao residues

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