National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Biodegradation of bioplasts in compost environment
Vodička, Juraj ; Kovalčík, Adriána (referee) ; Obruča, Stanislav (advisor)
This master’s thesis focuses on biodegradation of polyhydroxybutyrate (PHB) and polylactic acid (PLA). The theoretical part discusses an origin, properties and applications of investigated biopolyesters, and so the enzymology of their biodegradation. The experimental part deals with biodegradation of these polymers in liquid medium using several pure thermophilic bacteial strains and controlled composting of these bioplastics. Amongst six tested thermophilic bacterial strains only one showed PHB-biodegradation activity – strain Schlegelella thermodepolymerans. No degradation degree of amorphous or semi-crystalline PLA was observed. Mainly disintegration of both forms of PLA articles was observed in compost environment, thus the abiotic mechanism of its decomposition was indicated. After 4 weeks of composting, the relative weight loss of 99 % and 63 % was detected in amorphous and semi-crystalline PLA respectively. On the contrary, the weight loss of PHB after 4 weeks of composting reached 36 %, moreover, a half decrease of molar mass was observed using SEC. The surface erosive mechanism of PHB-biodegradation was stated using SEM. By monitoring of esterase, lipase and protease activities, no influence on the compost by polymer presence was concluded at statistical significance.
Polyhydroxyalkanoates as metabolites of prokaryotic microorganisms adapted to extreme conditions
Vodička, Juraj ; Slaninová, Eva (referee) ; Obruča, Stanislav (advisor)
The objective of this work is a study of polyhydroxyalkanoates as bacterial carbon and energy storage forms, which are produced intracellularly. The theoretical part of the study is focused on physical properties of PHA, their biotechnological production and degradation. The experimental part deals with production of polyhydroxyalkanoates by halophile bacterium Halomonas organivorans using several different carbon substrates. Firstly, the gene encoding for PHA-synthase, phaC, was successfully amplified and detected. Extracellular lipolytical activity was also proved. Secondly, the most appropriate substrate for bacterial growth and PHA production were found to be hydrocarbons, especially galactose and mannose. Due to these results, it is highly desirable to use coffee grounds for the biotechnological production of PHB, as galactomannan-rich waste. On the other hand, lactose and xylose have shown to be unsuitable carbon sources. For that reason, waste whey and lignocellulosic materials rich for pentoses are inconvenient substrates for the intended purpose. There is a potential use of waste molasses because of good results of sucrose at contrast. By the cultivation on kitchen waste and waste glycerol were the growth slow and the production of PHA reduced significantly. The optimal salt concentration for bacterial growth and PHA production were discovered as 60 grams per litre. Addition of several precursors of 3-hydroxyvalerate after 24 hours of cultivation have not induced the copolymer P(3HB-co-3HV) formation. Even though these precursors have inhibited the bacterial growth, the significant increase of the PHB percent contend was observed. In general, the yield of the production has been considerable, it should be noted than almost in each successful cultivation the PHA content in bacterial cells exceeded 50 weight %. With a respect to results, more experiments for full evaluation of H. organivorans as a potential biotechnological PHA producing bacteria are regarded.

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