Ammonium bicarbonate supplementation as carbon source in alkaliphilicSpirulinamass culture

Abstract

Cyanobacterium Spirulina (Arthrospira) platensis is a commercial product with high content of protein and other nutritional elements, serving as a source of nutrients for food, feed and pharmaceutical industry. Generally, CO2 gas bubbling method is a common method to supply carbon source for algae culture. However, in commercial situation where the CO2 supply is limited, alternative bicarbonate could be utilized as a substitute carbon source in Spirulina cultivation. In this study, the optimum culture method of ammonium bicarbonate supplementation in open raceway pond as carbon source was firstly investigated to avoid the inhibition effect of ammonium bicarbonate. The optimal conditions estimated by experimental results for S. platensis cultivation were set as following: (1) the addition of ammonium bicarbonate at each time must be <2.0 mmol L−1; (2) the addition rate of ammonium bicarbonate is in the range of 10–20 g m−2 day−1. Then, S. platensis were cultured in eight 800 m2 raceway ponds with fed-batch addition of ammonium bicarbonate combined with sodium bicarbonate as carbon source. The results illustrated that ammonium bicarbonate addition not only did not show any adverse impact on productivity, chlorophyll and carotenoid content of S. platensis, but also significantly increased the protein content of S. platensis. With ammonium bicarbonate supplementation as carbon source in alkaliphilic Spirulina mass culture, the carbon utilization efficiency was dramatically increased to approximately 70% from 38.89%, and the carbon cost was reduced by approximately 57%. Therefore, ammonium bicarbonate can be applied as supplement of carbon source for alkaliphilic Spirulina culture.