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Polyβ-hydroxybutyrate (PHB) is a heavy, molecular-weight polymer with monomer units of (R)-3-hydroxylbutyric acid (HBA) which is deposited as a storage component in many groups of microbes, and is an ecofriendly thermoplastic. Distillery spent wash (DSW) is an industrial waste which has elevated chemical oxygen demand (COD) levels but consists of valuable minerals that can be used for PHB production. Azotobacter vinelandii (ATCC® 12837™ and ATCC 13705™) was used to develop A. vinelandii UWD, which is a hyper PHB-producing mutant, by using N-methyl-N'-nitro- N-nitrosoguanidine (NTG) mutagenesis. This strain was grown in a fed-batch bioreactor containing diluted DSW at (1-7%) with 5% glucose as the carbon source, and ammonium acetate as the nitrogen source. The transformation efficiency for rifampicin (Rif)-positive colonies was 9 x 10 5 which was good enough to select the hyper PHB-producing mutants after five days of incubation. The amount of PHB produced in different dilutions of spent wash was highest (40g/L, 92%w/w) with 4% spent wash. The glucose consumption was 89% w/w at 4% DSW, and the dry cell weight was > 23.4 g/L. In addition, elevated COD levels ( 1100 mg/L) of DSW were decreased to 200 mg/L after fermentation was completed. The spent wash, which is considered to be a production waste and ecological pollutant, can be consequently used for bioplastic production. [ABSTRACT FROM AUTHOR]