ITA. “Sintesi microbica di poliidrossialcanoati (PHA) da fermentato di fanghi di depurazione” ENG. "Microbial synthesis of polyhydroxyalkanoates (PHA) from sewage sludge fermentation liquids"

Abstract

Objectives of the thesis. Management and monitoring of a pilot scale process for the microbial synthesis of intracellular biopolymer (polyhydroxyalkanoates, PHA) by using the fermentation liquids of municipal sewage sludge as carbon source.

Working methodology. The work is based on pilot-scale aerobic process, investigating the possibility to use a real feedstock, the fermented stream rich in volatile fatty acids (VFA) obtained by the anaerobic fermentation process of sewage sludge. The process needs to be judged in terms of stability and technical feasibility, as well as maximum PHA accumulation capacity of the mixed microbial culture PHA-producer.

Experimental part planned. Long-term pilot scale aerobic process (3-4 month) for the cultivation of a mixed microbial consortia highly enriched in PHA-accumulating microorganisms; the cultivated biomass will be evaluated in terms of storage response parameters (PHA storage yield; PHA storage rate). The process needs to be also evaluated in terms of robustness and stability, for its application at larger scale. Medium-low organic loading rate (OLR) and short hydraulic retention time (HRT) will be applied to sustain a good selection on PHA-storing biomass. This biomass will be tested in its accumulation capacity in order to quantify the maximum PHA content in the biomass. A final mass balance will be also assessed as first step for future technical-economic analysis of the technology.

Research area. Chemical plants (09 / D3) - Industrial biochemical processes

Expected results. The selection of PHA-storing biomass will be evaluated in terms of: a) storage rate (expected values 200-300 mgPHA/(gX h)), b) storage yield (expected value 0.4-0.6 gPHA/gVFA). The accumulation potential of the biomass could be around 40-50% of PHA as percentage in terms of cell dry weight (w/w). The last part of the thesis will be dedicated to the calculation of the overall yield, as gPHA per g of Carbon Source. This value is pivotal for the technical-economical evaluation of the technology.

Dated: 04th March 2021