Biorefinery concept for Cylindrospermum alatosporum CCALA 988 extracting multiple high-value compounds and residue utilization by P. pastoris fermentation producing phytase

Abstract

Economically feasible biorefinery concepts rely on the production of multiple high-value products and valorization even of residual side streams. This generally holds true for biomass from agriculture, forestry, and aquaculture. Cyanobacteria are seen as promising organisms for this purpose. The potential for commercialization, however, strongly depends on the strain being used and the range of products it offers. The cyanobacterial strain Cylindrospermum alatosporum CCALA 988 was reported to produce high amounts of the cyclic lipopeptides puwainaphycins (PUWs) and minutisamides (MINs) as high-value products. Hence, this study investigated the biomass of the cyanobacterial strain as a potential feedstock for a biorefinery concept. The study also explored the enzymatic hydrolysis of the residual biomass and its utilization as a medium supplement for appA E. coli phytase expression with Pichia pastoris. Analysis of the cyanobacterial biomass revealed the following composition: ash 1.9 %, lipids 4.1 %, starch 2.4 %, structural saccharides 8.7 %, and protein 52.4 %. Further, a sequential extraction concept and a bench-scale mass balance were investigated, and products were proposed with 56.2 % of biomass being utilized and 43.8 % being left as residue. PUWs (21.6 mg/g), MINs (101.5 mg/g), phycobiliproteins (34.5 mg/g), and pigments (6.4 mg/g) were selected as products and quantified. The utilization of hydrolysate by fermentation of P. pastoris for appA E. coli phytase expression was studied in a 1 L system. In batch mode, the hydrolysate allowed to achieve comparable results to a rich complex medium, with over 500 U/mL of appA E. coli phytase. The obtained results provide a basis for further development of this biorefinery concept.