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1

The synthesis of polyhydroxyalkanoates by activated sludge

100%
Klimiuk E., Pokoj T.
Biotechnologia
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2008
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issue 3
9-27
EN
Polyhydroxyalkanoates are polyesters insoluble in water, synthesized by microorganisms and accumulated intracellular as storage materials. They are marked by high degree of polimerization, non-toxicity, wide range of application and biodegrability. Until now, there have been applied mainly pure microbial cultures for industrial PHAs production. Currently, for that purpose there are conducted intensive investigations on use of mixed microbial cultures (activated sludge). The microorganisms of activated sludge accumulate polyhydroxyalkanoates as storage materials when availability of organics as electron donors and oxygen or nitrate (electron acceptors) is distributed in time and space or when the sludge is submitted to consecutive periods of external substrate accessibility and unavailability. The process efficiency depends on feed composition and reactor operating conditions. Nowadays, there are two types of reactor operational strategies. In municipal wastewater treatment plants, a two-stage process is used: 1 ? selection of excess sludge to specific type of substrate (molesses, whey) in SBR, and 2 ? PHAs production in batch reactor. In wastewater treatment plants from agricultural and food industry, acidogenic fermentation is introduced as an additional stage, where the organic wastes are converted into a mixture of organic acids, and then used as a substrate for PHAs storage.
2

Accumulation of polyhydroxyalkanoates (PHAs) in activated sludge under nitrogen limitation conditions. Part I. Effect of operational condition on effectiveness of poly(3-hydroxybutyric acid) (P(3HB)) accumulation

81%
Pokoj T., Klimiuk E., Kuczajowska-Zadrozna M.
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|
issue 4
197-213
EN
The accumulation of poly(3-hydroxybutyric acid) in activated sludge was investigated. Fed-batch culture was carried out using sodium acetate as the source of carbon. A lack of nitrogen was a stimulating factor of accumulation P(3HB). Two experimental series were run. In series 1, nitrogen was fed into abacterial culture once for the first 24 hours, in series 2 ? for 6 hours each day of the experiment. The effect of operational conditions was evaluated based on the accumulation of P(3HB) in biomass, specific growth rate of microorganisms (m) yield coefficients (YP(3HB)/C, YP(3HB)/X), and productivity P(3HB). It was proved that the degree of accumulation of P(3HB) in activated sludge was comparable in both series. The highest P(3HB) yield of 0.59 g P(3HB)/g COD was attained in series 1 at the 12 th our after ceasing the nitrogen feeding. In series 1, between the 36 th and 48 th hour, the productivity reached the level of about 34 mg P(3HB)/l?h). In series 2, YP(3HB)/C and the productivity accounted for 0.21 g P(3HB)/g ChZT and 21.58 mg P(3HB)/l?h, respectively. The limiting factor of P(3HB) productivity was low specific growth rate of microorganisms of activated sludge. The maximum specific growth (max) reached 0.03 h-1 in series 1 and 0.022h-1 in series 2.
3

Accumulation of polyhydroxyalkanoates (PHAs) in activated sludge under nitrogen limitation conditions. Part II. Estimation of bacterial diversity in activated sludge and analysis of a type of accumulated polyhydroxyalkanoates

81%
Klimiuk E., Ciesielski S., Pokoj T., Rogowski J.
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|
issue 4
214-226
EN
Community diversity of the activated sludge and the type of accumulated PHAs were investigated in this study. Fed-batch culture was carried out using medium culture containing sodium acetate as a carbon source. A factor triggering PHAs synthesis was a lack of nitrogen. The medium culture containing ammonium was periodically fed into bacterial culture for 6 hours each day of the experiment. Genetic analysis of the bacterial community was performed using 16S and 23S rRNA Intergeneric Spacer Region. The obtained results showed that the dominant belonged to the Betaproteobacteria class. In this study, the Time of flight - Secondary Ion Mass Spectrometry was used. This method revealed that the cells of the microorganisms contained mainly monomer units of 3-hydroxybutryric acid. The content of P(3HB) in dry weight accounted for 51% between 72nd and 120th hour of the experiment.
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