Influence of the cycle length on the production of PHA and polyglucose from glycerol by bacterial enrichments in sequencing batch reactors

Abstract

PHA, a naturally occurring biopolymer produced by a wide range of microorganisms, is known for its applications as bioplastic. In recent years the use of agro-industrial wastewater as substrate for PHA production by bacterial enrichments has attracted considerable research attention. Crude glycerol as generated during biodiesel production is a waste stream that due to its high organic matter content and low price could be an interesting substrate for PHA production. Previously we have demonstrated that when glycerol is used as substrate in a feast-famine regime, PHA and polyglucose are simultaneously produced as storage polymers. The work described in this paper aimed at understanding the effect of the cycle length on the bacterial enrichment process with emphasis on the distribution of glycerol towards PHA and polyglucose. Two sequencing batch reactors where operated with the same hydraulic and biomass retention time. A short cycle length (6 h) favored polyglucose production over PHA, whereas at long cycle length (24 h) PHA was more favored. In both communities the same microorganism appeared dominating, suggesting a metabolic rather than a microbial competition response. Moreover, the presence of ammonium during polymer accumulation did not influence the maximum amount of PHA that was attained.

Nutrient removal via nitrite from reject water and polyhydroxyalkanoate (PHA) storage during nitrifying conditions

“…Figure shows the depletion of SCFAs over time for the four cases examined. In all four cases, the uptake rate of SCFAs was comparable and in the range 0.08–0.10 C‐mmol/C‐mmol h. The F/M ratio plays an important role during enrichment of the bacterial community . In this study, the uptake rate of the total SCFAs derived from the SFL was not significantly affected by the F/M.…”

“…However, the authors enhanced the quality of the carbon source by removing nitrogen and phosphorus as struvite. The yields of the PHA, PHB and PHV produced in the present work were calculated on the basis of SCFAs uptake and are given in Table in comparison with existing literature data . Figure shows the depletion of SCFAs over time for the four cases examined.…”

“…However, the plant was not optimized for nutrient removal and a post treatment was required. Several parameters have been reported to affect the PHA storage yield and productivity, such as the solids retention time (SRT), the feast‐famine regime (meaning the alternation of high (feast) and low (famine) substrate availability) the feeding regime (ratio of feeding duration to the total cycle duration), the organic loading rate, the C/N ratio, the type of carbon source that is supplied, and the cycle length . The potential for integrating nitritation and PHA production has not been previously studied, and is of considerable interest since it could promote simultaneous nutrient removal with the recovery of a value‐added product (PHA).…”

Value-Added Products Derived from Waste Activated Sludge: A Biorefinery Perspective

“…Literature-reported experimental (laboratoryscale) conditions for PHA production from WAS-derived media are summarised in Table 5. At present, sequencing batch reactors are reported to be promising for enhanced PHA production, due to their highly flexible operation, ease of process control and biomass growth under transient conditions [95,96]; however, full-or pilot-scale studies are rarely reported in the literature [50]. The major technical challenge associated with bioplastics production from WAS remains the economically lower yields [97], which requires extensive studies on the optimisation of organic loading rate and efficacy of utilising mixed substrates (e.g., sewage sludge and agroindustry wastewater sludge) with mixed cultures.…”

Biopolymer production using fungus Mucor racemosus Fresenius and glycerol as substrate

“…Researchers are seeking an alternative for the bioconversion of this by-product. According to Moralejo-Garate et al [1] the crude glycerol is a by-product of the biodiesel industry and a potentially good substrate for the production of biopolymers.…”