Using inorganic acids to stop purple phototrophic bacteria metabolism improves PHA recovery at a large scale

Abstract

Polyhydroxyalkanoate (PHA) production at a large scale by purple phototrophic bacteria (PPB) is hindered due to high production costs and limited recovery due to its consumption during starvation periods. The present study identified cost-effective inorganic acids as inactivation methods for PPB to obtain higher PHA recovery. The study was performed on reactors of different scales (10 L and 0.5 L) to grow PPB and recover PHA subsequently. The permanent feast strategy was adopted to obtain higher PHA in an anaerobic environment. As a result, the study achieved 33% (dry weight) PHA recovery using inorganic acid inactivation, while formaldehyde inactivation (traditional method) achieved significantly lower PHA recovery (20% only). The results from inorganic acid inactivation were further examined for their stability. The samples were stable even after day 14, and the PHA recovery was the same as on day 0. This pioneering study shows that inorganic acids can be used to inactivate the PPB metabolism to obtain higher PHA recovery; inorganic acid inactivation could be economical for large-scale PHA production. Graphical Abstract

A review on microbes mediated resource recovery and bioplastic (polyhydroxyalkanoates) production from wastewater

“…Phosphorus and nitrogen removal efficiencies were 83.55% and 79.36% 42.28 - [ 173 ] Haloferax mediterranei Sesame seed wastewater 5 L Mixing rate 230 rpm, at 37 °C for 4 d, pH 7.0, aeration 0.75 VVM 6 g.L − 1 yeast extract and 100 g.L − 1 NaCl was optimum for PHA accumulation. 75 0.53 [ 83 ] Mixed inoculum Wastewater 10 L Volatile suspended solids 100 mg L − 1 ; Temp 24 ± 4 °C; dissolved oxygen < 0.2 mg L − 1 ; pH 7 and time 5 days Inorganic acid inactivation of metabolism increased the yield from 20–33% 35–38 - [ 174 ] Pseudomonas mendocina CH50 Waste frying oil 14 L Temp 30 °C, mixing rate 200 rpm, air flow 1 vvm, and time 48 h Biomass accumulation 1.03 g.L − 1 AuNPs/PHA composite reduced viral infectivity against SARS-CoV-2 pseudotype virus by 75%. − 0.23 [ 175 ] Microalgae Aquaculture effluent 22 L pH 6.8; period 14 d; The high light intensity increased PHB accumulation while biomass yield lowered; no effect of light on lipid content; low-intensity red light was carbon neutral.…”

“… 20% - - Comparatively economic and can be used at a higher scale as well accumulation was 33% dry cell weight. [ 174 ] PHARIO project activated sludge - Extraction with 10 mL dimethyl carbonate at 125 o C for 60 min. 100% 95 ± 2 - Thermal treatment of dry PHA-rich biomass lowers PHA molecular weight predictably.…”