Abstract
Background: Unlike petroleum-based synthetic plastics, biodegradable biopolymer generation from industrial residue is a key strategy to reduce costs in the production process, as well as in the waste management, since efficient industrial wastewater treatment could be costly. In this context, the present work describes the prospection and use of bacterial strains capable to bioconvert cassava starch by-product into biodegradable polyhydroxyalkanoates (PHAs). Results: The first step of this study was the bacterial competence screening which was conducted with 72 strains covering 21 Bacillus and related species. The microorganism growth in a medium with a starch substrate was measured by an innovative MTT assay, while the ability of the bacteria to secrete amylase and produce PHA was evaluated by the Nile Red Dye method. Based on growth and potential for PHA production, four isolates were selected and identified as Bacillus megaterium by 16S rRNA sequencing. When cultivated in hydrolyzed cassava starch by-product, maximum production reached 4.97 g dry biomass/L with 29.7% of Poly-(3-hydroxybutyrate) (characterized by FTIR). Conclusions: MTT assay proved to be a reliable methodology for monitoring bacterial growth in insoluble media. Selected amylolytic strains could be used as an alternative industrial process for biodegradable plastics production from starchy residues, reducing costs for biodegradable biopolymer production and wastewater treatment operations.
Highlights
Polymeric materials are important for society due to their characteristics of versatility, durability and resistance to degradation
The microorganism growth in a medium with a starch substrate was measured by an innovative MTT assay, while the ability of the bacteria to secrete amylase and produce PHA was evaluated by the Nile Red Dye method
Selected amylolytic strains could be used as an alternative industrial process for biodegradable plastics production from starchy residues, reducing costs for biodegradable biopolymer production and wastewater treatment operations
Summary
Polymeric materials are important for society due to their characteristics of versatility, durability and resistance to degradation. PHAs are accumulated intracellularly by bacteria as carbon or energy reserves, mainly when there is a limitation of an essential nutrient, such as nitrogen, phosphorus, oxygen or sulphur (Verlinden et al 2007) Due to their chemical and physical characteristics, PHAs have a wide range of applications including conventional plastic materials, utensils, and cosmetic containers, as well as in medicine (as bone plates, surgical sutures and blood vessel replacements), in the pharmaceutical and food industries, and as biodegradable carriers for the long-term dosage of drugs, medicines, hormones, insecticides and herbicides (Reddy et al 2003). Unlike petroleum-based synthetic plastics, biodegradable biopolymer generation from industrial residue is a key strategy to reduce costs in the production process, as well as in the waste management, since efficient industrial wastewater treatment could be costly In this context, the present work describes the prospection and use of bacterial strains capable to bioconvert cassava starch by-product into biodegradable polyhydroxyalkanoates (PHAs). Selected amylolytic strains could be used as an alternative industrial process for biodegradable plastics production from starchy residues, reducing costs for biodegradable biopolymer production and wastewater treatment operations
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