Production of polyhydroxybutyrates and carbohydrates in a mixed cyanobacterial culture: effect of nutrients limitation and photoperiods

TL;DR

This study investigates how different light cycles and nutrient limitations affect the production of bioplastics and biofuel precursors in wastewater cyanobacteria, finding optimal conditions for maximum accumulation.

Contribution

It provides new insights into optimizing nutrient and light conditions to enhance PHB and carbohydrate production in mixed cyanobacterial cultures.

Findings

Maximum PHB (104 mg/L) under P limitation with continuous light.

Maximum carbohydrate (838 mg/L) under N limitation with light/dark cycles.

Nutrient limitation enhances bioplastic and biofuel precursor accumulation.

Abstract

In the present study, different photoperiods and nutritional conditions were applied to a mixed wastewater-borne cyanobacterial culture in order to enhance the intracellular accumulation of polyhydroxybutyrates (PHBs) and carbohydrates. Two different experimental set-ups were used. In the first, the culture was permanently exposed to illumination, while in the second; it was submitted to light/dark alternation (12h cycles). In both cases, two different nutritional regimes were also evaluated, N-limitation and P-limitation. Results showed that the highest PHB concentration (104 mg L-1) was achieved under P limited conditions and permanent illumination, whereas the highest carbohydrate concentration (838 mg L-1) was obtained under N limited condition and light/dark alternation. With regard to bioplastics and biofuel generation, this study demonstrates that the accumulation of PHBs (bioplastics) and carbohydrates (potential biofuel substrate) is favored in wastewater-borne cyanobacteria under conditions where nutrients are limited.