Browsing by Subject "jätevesiliete"

The use of plastics has increased globally and more and more of it ends up in the environment. Microbes can be used to produce polyhydroxyalkanoates (PHA), a biodegradable plastic substrate. Instead of nonrenewable fossil raw materials, such as renewable sewage sludge can be used as a carbon source for polyhydroxyalkanoates. The aim of this work was to investigate the microbial diversity and metabolism of the first hydrolysis step of the three-step polyhydroxyalkanoate (PHA) production process. In the first step, organic polymers, such as carbohydrates, lipids and proteins are hydrolyzed into monomers, which are then converted into short-chain volatile fatty acids (VFA). The volatile fatty acids are used in the third step as a substrate in microbial PHA production. In the second step, the polyhydroxyalkanoates accumulating microbes are enriched, and used in the third step for PHA synthesis. In this work, different types of sludges were used as a carbon source. Sludges were sludge for biogas production, sludge after biogas production and sludge after nitrogen removal in stripping. The concentration of volatile fatty acids, cellulose and lignin was determined in the bioreactors. Volatile fatty acids were determined by gas chromatography. Cellulose and lignin were determined after hydrolysis by filtering and drying the samples. The nucleotide sequence of the 16S rRNA gene was determined from pure materials. Shotgun metagenome sequencing was performed on bioreactor DNA samples to sequence the entire microbial genomes. Hydrolysis bioreactors were maintained for 12 days. Microbes did not degrade cellulose and lignin well. The best volatile fatty acids yields were obtained from the sludge for biogas production (172 mg/g organic matter ± 6.25). Proteobacteria and Firmicutes were the major phyla in the bioreactors, and microbial genera differed greatly between bioreactors. Microbial genes coding for carbohydrate and protein metabolism were predominant in the bioreactors.