Abstract
Polyhydroxyalkanoates (PHAs) are biodegradable and biocompatible plastics. They are synthesized by a wide variety of microorganisms (i.e., fungi and bacteria) and some organisms such as plants, which share characteristics with petrochemical-based plastics. The most recent studies focus on finding inexpensive substrates and extraction strategies that allow reducing product costs, thus moving into a widespread market, the market for petroleum-based plastics. In this study, the production of polyhydroxybutyrate (PHB) was evaluated using the native strains,Bacillus megaterium,Bacillussp., andLactococcus lactis, and glycerol reagent grade (GRG), residual glycerol (RGSB) byproduct of biodiesel from palm oil, Jatropha oil, castor oil, waste frying oils, and whey as substrates. Different bacteria-substrate systems were evaluated thrice on a laboratory scale under different conditions of temperature, pH, and substrate concentration, employing 50 mL of broth in 250 mL. The bacterial growth was tested in all systems; however, theB. megateriumGRG system generated the highest accumulation of PHA. The previous approach was allowed to propose a statistical design optimization with RGSB (i.e., RGSB, 15 g/L, pH 7.0, and 25°C). This system reached 2.80 g/L of PHB yield and was the optimal condition tested; however, the optimal biomass 5.42 g/L occurs at pH 9.0 and 25°C, with a substrate concentration of 22 g/L.
Highlights
Biopolymers are macromolecules produced by living cells from renewable sources, which give rise to known biodegradable plastics and can be an alternative to solve environmental and social problems generated by the plastics industry from petrochemicals.The petroleum-based plastics are highly resistant to temperature, pressure, chemical solvents, UV light, among other factors, which are widely employed in all fields of industry
All substrates tested were suitable for the growth of the strains B. megaterium, Bacillus sp., and L. lactis; the low biomass concentrations obtained for some systems are an obstacle for PHA production
B. megaterium strain has the property of growing in sugar substrates, oily substrates, and glycerol; the latter has the advantage of producing PHB in amounts similar to those produced from sugar residues, under the operating conditions used in this experiment
Summary
Biopolymers are macromolecules produced by living cells from renewable sources, which give rise to known biodegradable plastics and can be an alternative to solve environmental and social problems generated by the plastics industry from petrochemicals.The petroleum-based plastics are highly resistant to temperature, pressure, chemical solvents, UV light, among other factors, which are widely employed in all fields of industry. Biopolymers are macromolecules produced by living cells from renewable sources, which give rise to known biodegradable plastics and can be an alternative to solve environmental and social problems generated by the plastics industry from petrochemicals. The plastics production scale (with an annual increase close to 6.5% during the 5 years) is exponential accumulation of plastic waste in the environment [2] and pollution of water bodies and soils. This has a negative impact on human health, turning them into a social problem of high interest [3]. Researchers around the world have focused on the production of biodegradable polymers in the recent decades, using different methods and procedures, mainly in the family of the polyhydroxyalkanoates (PHA) and its derivatives thereof (e.g., polylactic polyesters aliphatic, polysaccharides) [4]
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