Aerobic and anaerobic microbial degradation of poly-beta-hydroxybutyrate produced by Azotobacter chroococcum |
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Authors: | Bonartseva G A Myshkina V L Nikolaeva D A Kevbrina M V Kallistova A Y Gerasin V A Iordanskii A L Nozhevnikova A N |
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Institution: | (1) Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr. 33, 119071 Moscow, Russia;(2) Institute of Microbiology, Russian Academy of Sciences, Prospect 60-letiya Octyabrya 7, k. 2, 117811 Moscow, Russia;(3) Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninskii pr. 29, 117912 Moscow, Russia;(4) Semenov Institute of Chemical Physics, Russian Academy of Sciences, Kosygina str., 4, 119991 Moscow, Russia |
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Abstract: | Food industry wastewater served as a carbon source for the synthesis of poly-β-hydroxybutyrate (PHB) by Azotobacter chroococcum. The content of polymer in bacterial cells grown on the raw materials reached 75%. PHB films were degraded under aerobic,
microaerobic, and anaerobic conditions in the presence and absence of nitrate by microbial populations of soil, sludges from
anaerobic and nitrifying/denitrifying reactors, and sediment from a sludge deposit site. Changes in molecular mass, crystallinity,
and mechanical properties of PHB were studied. Anaerobic degradation was accompanied by acetate formation, which was the main
intermediate utilized by denitrifying bacteria or methanogenic archaea. On a decrease in temperature from 20 to 5° C in the
presence of nitrate, the rate of PHB degradation was 7.3 times lower. Under anaerobic conditions and in the absence of nitrate,
no PHB degradation was observed, even at 11°C. The enrichment cultures of denitrifying bacteria obtained from soil and anaerobic
sludge degraded PHB films for a short time (3–7 d). The dominant species in the enrichment culture from soil were Pseudomonas fluorescens and Pseudomonas stutzeri. The rate of PHB degradation by the enrichment cultures depended on the polymer molecular weight, which reduced with time
during biodegradation. |
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Keywords: | Aerobic microaerobic and anaerobic conditions Azotobacter chroococcum denitrification denitrifying microorganisms methanogenesis microbial degradation poly-β -hydroxybutyrate |
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