In this study we investigated the feasibility of producing polyhydroxyalkanoate (PHA) by
microbial enrichments on paper mill wastewater. The complete process includes (1) paper
mill wastewater acidogenic fermentation in a simple batch process, (2) enrichment of
a PHA-producing microbial community in a selector operated in sequencing batch mode
with feast-famine regime, (3) Cellular PHA content maximization of the enrichment in an
accumulator in fed-batch mode. The selective pressure required to establish a PHAproducing
microbial enrichment, as derived from our previous research on synthetic
medium, was validated using an agro-industrial waste stream in this study. The microbial
enrichment obtained could accumulate maximum up to 77% PHA of cell dry weight within
5 h, which is currently the best result obtained on real agro-industrial waste streams,
especially in terms of biomass specific efficiency. Biomass in this enrichment included
both Plasticicumulans acidivorans, which was the main PHA producer, and a flanking population,
which exhibited limited PHA-producing capacity. The fraction of P. acidivorans in
the biomass was largely dependent on the fraction of volatile fatty acids in the total soluble
COD in the wastewater after acidification. Based on this observation, one simple equation
was proposed for predicting the PHA storage capacity of the enrichment. Moreover, some
crucial bottlenecks that may impede the successful scaling-up of the process are discussed
In this study we investigated the feasibility of producing polyhydroxyalkanoate (PHA) bymicrobial enrichments on paper mill wastewater. The complete process includes (1) papermill wastewater acidogenic fermentation in a simple batch process, (2) enrichment ofa PHA-producing microbial community in a selector operated in sequencing batch modewith feast-famine regime, (3) Cellular PHA content maximization of the enrichment in anaccumulator in fed-batch mode. The selective pressure required to establish a PHAproducingmicrobial enrichment, as derived from our previous research on syntheticmedium, was validated using an agro-industrial waste stream in this study. The microbialenrichment obtained could accumulate maximum up to 77% PHA of cell dry weight within5 h, which is currently the best result obtained on real agro-industrial waste streams,especially in terms of biomass specific efficiency. Biomass in this enrichment includedboth Plasticicumulans acidivorans, which was the main PHA producer, and a flanking population,which exhibited limited PHA-producing capacity. The fraction of P. acidivorans inthe biomass was largely dependent on the fraction of volatile fatty acids in the total solubleCOD in the wastewater after acidification. Based on this observation, one simple equationwas proposed for predicting the PHA storage capacity of the enrichment. Moreover, somecrucial bottlenecks that may impede the successful scaling-up of the process are discussed
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