Growth and phycocyanin synthesis in the heterotrophic microalga Galdieria sulphuraria on substrates made of food waste from restaurants and bakeries

Galdieria sulphuraria 074G (Rhodophyta) was grown heterotrophically in defined medium and on amylolytic and proteolytic hydrolysed food waste from restaurants and bakeries. Substrate uptake, growth, and phycocyanin content were quantified in the cultures. The alga utilised carbohydrates and amino acids from the waste but ammonium and other inorganic nutrients were needed to stimulate phycocyanin synthesis. Highest specific phycocyanin contents (20–22 mg g−1) were observed in cells grown at 25 °C or 34 °C on the food wastes. Growth inhibition was observed when the hydrolysates were used in quantities resulting in glucose concentrations of 10 and 50 g L−1 for bakery and restaurant waste, respectively. Still, G. sulphuraria 074G grew and produced phycocyanin efficiently on food waste under adequate conditions and may potentially be utilised for synthesise of high-valuable products from food waste.