Abstract
Being biodegradable and biocompatible natural polymer, poly-β-hydroxybutyrate (PHB) drew the attention of scientists to substitute synthetic plastics in our daily lives. However, its industrial production is hampered by its high cost. In this study, an extensive screening program was done to isolate bacteria with high PHB productivity from agricultural fields and develop a cost-effective PHB production. A promising bacterial isolate Acinetobacter baumannii P39 was recovered and identified using 16S ribosomal gene sequencing. It produced 24% PHB per dry weight after 48 h. Several experiments were conducted to optimize the composition of the culture medium and environmental factors for the selected isolate. Results revealed that 60% aeration, 28°C incubation temperature and initial pH 7.5 showed the highest productivity. Besides, 0.7% corn oil and 0.1 g/L peptone were the best carbon and nitrogen sources, respectively. Substituting glucose with corn oil led to a 23% reduction in total input cost and an estimate price for 1kg PHB is 20.5 L.E. Strain improvement by UV mutation succeeded in improving PHB production by two fold in the selected mutant P39M2. Finally, this study valorizes usage of Acinetobacter isolate in PHB production in addition to solving the critical problem of high cost of production.
Highlights
Biodegradable plastics are the ultimate solution for the everlasting problem of synthetic plastic wastes and its deleterious effect on environment (Poirier et al, 1995; Mecking, 2004)
As shown in figure (1), maximum PHB percentage per dry weight occurred at 60% aeration while maximum biomass in terms of dry weight occurred using 80% aeration
After implementing all of the optimum factors in the new medium 39M, Maximum PHB percentage per dry weight occurred after 48 h (28%)
Summary
Biodegradable plastics are the ultimate solution for the everlasting problem of synthetic plastic wastes and its deleterious effect on environment (Poirier et al, 1995; Mecking, 2004). Biodegradable plastics, bioplastics, bacterial thermoplastic and green polymers all are names given to family of polyhydroxyalkanoates (Holmes, 1985; Poirier et al, 1995; Luengo et al, 2003). They have the same characteristics of synthetic plastics in addition to biodegradability and biocompatibility (Luckachan and Pillai, 2011). Polyhydroxybutyrate (PHB) is the most abundant and well characterized member in polyhydroxyalkanoates (PHA) family It has a widespread appearance in both Gram positive and Gram negative organisms (Senior et al, 1972). By comparing the PHB production among positive isolates, Acinetobacter baumanii isolate P39 produced the highest PHB percentage per dry weight among tested Gram negative isolates. The aim of this study was to shine a new light on cost-effective PHB production using Acinetobacter baumannii
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