Accumulation of polyhydroxyalkanoates by Microlunatus phosphovorus under various growth conditions

Abstract

Microlunatus phosphovorus is an activated-sludge bacterium with high levels of phosphorus-accumulating activity and phosphate uptake and release activities. Thus, it is an interesting model organism to study biological phosphorus removal. However, there are no studies demonstrating the polyhydroxyalkanoate (PHA) storage capability of M. phosphovorus, which is surprising for a polyphosphate-accumulating organism. This study investigates in detail the PHA storage behavior of M. phosphovorus under different growth conditions and using different carbon sources. Pure culture studies in batch-growth systems were conducted in shake-flasks and in a bioreactor, using chemically defined growth media with glucose as the sole carbon source. A batch-growth system with anaerobic-aerobic cycles and varying concentrations of glucose or acetate as the sole carbon source, similar to enhanced biological phosphorus removal processes, was also employed. The results of this study demonstrate for the first time that M. phosphovorus produces significant amounts of PHAs under various growth conditions and with different carbon sources. When the PHA productions of all cultivations were compared, poly(3-hydroxybutyrate) (PHB), the major PHA polymer, was produced at about 20-30% of the cellular dry weight. The highest PHB production was observed as 1,421 mg/l in batch-growth systems with anaerobic-aerobic cycles and at 4 g/l initial glucose concentration. In light of these key results regarding the growth physiology and PHA-production capability of M. phosphovorus, it can be concluded that this organism could be a good candidate for microbial PHA production because of its advantages of easy growth, high biomass and PHB yield on substrate and no significant production of fermentative byproducts.

A Critical Assessment of the Microorganisms Proposed to be Important to Enhanced Biological Phosphorus Removal in Full-Scale Wastewater Treatment Systems

“…Although some unidentified storage polymer was postulated, neither PHA nor glycogen cycling occurred and P and carbon metabolism were not exclusively coupled (Santos et al, 1999). The type strain reportedly lacks the genes for PHA synthesis (Kawakoshi et al, 2012), however, it has been reported to synthesize the storage polymer (Akar et al, 2006). The physiology of Microlunatus spp.…”

Extraction and Characterization of Polyhydroxybutyrates (PHB) from Bacillus thuringiensisKSADL127 Isolated from Mangrove Environments of Saudi Arabia

“…Many solid waste management programs have been conducted by various countries to reduce plastic waste and have come up with new ways to produce biodegradable plastic materials such as Polyhydroxybutyrates (PHBs). These are the natural biopolymers, that are synthesized and catabolized by microorganisms particularly bacteria (Witholt and Kessler 2002;Akar et al 2006;Berlanga et al 2006). There are more than 300 of such species known to produce PHB's (Berlanga et al 2006).…”

Extraction and characterization of PHB from Acidiphilium cryptum DX1-1

“…Producing plastics from materials that can be readily eliminated from our biosphere in an "environmentally friendly" fashion has attracted special interest [2] . Bioplastics are natural biopolymers that are synthesized and catabolized by various organisms [3,4] , and these materials do not cause toxic effects in the host and have certain advantages over petroleum-derived plastic [5] . Poly-β -hydroxybutyrate (PHB), a commonly used bioplastic, is a kind of polyester and homopolymer widely produced and naturally accumulated by a large number of bacteria as intracellular granules in response to unfavorable growth conditions and nutrient imbalance [6][7][8] .…”