Abstract
BackgroundMany waste streams have a relatively high vegetable oil content, which is a potential resource that should be recovered. Microbial storage compound production for the recovery of lipids from lipid-water emulsions with open (unsterilized) microbial cultures was investigated in a sequencing batch reactor using a diluted vegetable oil emulsion as model substrate.ResultsAfter feeding, triacylglycerides (TAG) were accumulated intracellular by the microbial enrichment culture and subsequently used for growth in the remainder of the sequencing batch cycle. Roughly 50% of the added TAG could be recovered as intracellular lipids in this culture. The maximum lipid storage capacity of the enrichment culture was 54% on volatile suspended solids (VSS) mass basis in a separate fed-batch accumulation experiment. The microbial community was dominated by a lipolytic fungus, Trichosporon gracile, that was responsible for intracellular lipid accumulation but also a significant fraction of lipolytic and long chain fatty-acid-utilizing bacteria was present.ConclusionHerewith, we demonstrate an effective strategy for enrichment of a microbial community that can accumulate significant amounts of lipids from wastewaters without the need for sterilization of substrates or equipment. Further optimization of this process will make recovery of lipids from wastewater possible.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0228-9) contains supplementary material, which is available to authorized users.
Highlights
The use of agro-industrial organic residues for the production of valuable commodities is a logical step towards a bio-based economy
It has been found that different carbon sources in a feast-famine process can result in formation of different storage compounds: microbial cultures enriched on glucose or starch, produced polyglucose as storage compound [10,11], a microbial culture enriched on glycerol produced a mixture of polyglucose and PHA [12], microbial communities enriched on different types of volatile fatty acids (VFA) produced different varieties of PHA [13,14], and a microbial culture enriched on methanol did not produce any storage compounds [15]
TOC measurements indicated that the carbon content of the organic solids in the effluent was 0.59 (±0.03) gC/gVSS resulting in a total organic solids production equivalent to 59 ± 10 Cmmol per cycle
Summary
The use of agro-industrial organic residues for the production of valuable commodities is a logical step towards a bio-based economy. A relatively well studied example of a process based on storage compound production by microbial enrichment cultures is the production of polyhydroxyalkanoate (PHA) and contents up to 90% on VSS mass basis have been obtained by application of selective pressure in the form of feast-famine conditions [5,6]. This process is currently further evaluated in industrial environments [7,8,9]. Microbial storage compound production for the recovery of lipids from lipid-water emulsions with open (unsterilized) microbial cultures was investigated in a sequencing batch reactor using a diluted vegetable oil emulsion as model substrate
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