This work aimed to study the feasibility of using vinasse for polyhydroxybutyrate (PHB) production by Bacillus megaterium. To optimize the culture medium, a Box–Behnken design was employed considering carbon (C), nitrogen (N), and phosphorus (Ph) concentrations as independent variables and PHB productivity as the response variable. The productivity decreased when C or N were increased, probably due to the presence of phenolic compounds and the limitation of N for the production of PHB by Bacillus sp. bacteria. An additional experimental design to optimize the C/N ratio and growing conditions (fermentation time and temperature) was carried out. Fermentation time had a statistically significant effect on PHB productivity reaching 10.6 mg/L h. On the other hand, the variability in physicochemical properties of vinasse samples led to significant differences in PHB productivity. Lower productivity values were obtained when vinasse had higher values of DBO. Therefore, biopolymers production from vinasse is a feasible alternative to valorize this bioethanol by-product.
Graphical Abstract
By-products of bioethanol production, such as vinasse can be transformed
by biotechnological processes into valuable compounds. In this work, the
economic feasibility of producing poly(hydroxyalcanoate)s (PHAs) from
vinasse and diverse microorganisms was studied employing a
superstructure whose objective function is the maximization of the Net
Present Value (NPV). The model was run employing data reported in the
literature about PHAs productivities obtained by using different
bacteria strains and vinasse as carbon source. Thus, comparison of
different scenarios is shown from techno-economic and environmental
aspects. Mathematical model estimated that PHA production cost was 2.27
- 3.02 USD and the investment resulted 9- 13 million dollars. The energy
consumption was also calculated and it was 13.8 - 21 MJ/Kg PHA. The
model returned NPV negative values in those scenarios with low
accumulation and low yield of PHAs, indicating that benefits are not
being obtained and, therefore, would not meet the expectations for an
investment project. Positive NPV values were obtained, being the highest
one 35.09 million dollars. Results evidenced that microorganism
selection, concentration of the pretreated vinasse, and inorganic salts
in the culture media would be the most relevant factors to take into
account when designing a PHA production plant.
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