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

[Display omitted] •A mixed culture dominated by cyanobacteria was enhanced to accumulate metabolites.•The effect of N and P limitation and two photoperiods were investigated.•P limitation with permanent light promoted the highest PHB concentration.•N limitation with alternate illumination leaded to the highest carbohydrates concentration. 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 (12 h 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.