Influence of environmental conditions on Nostoc sphaericum: physicochemical and functional characterization of exopolysaccharides using response surface methodology

Omote-Sibina J.R.; Chirinos R. · Applied Phycology (2026) · DOI: 10.1080/26388081.2026.2662292

Resumen

Nostoc sphaericum is an edible cyanobacterium with high nutritional and functional value, traditionally consumed in Peru since pre-Columbian times. It can produce exopolysaccharides (EPS), which remain poorly studied but have potential applications in various industries. The objective of this study was to determine the influence of environmental conditions on Nostoc sphaericum development and to optimize the extraction of the biopolymer and characterize it physically, chemically and techno-functionally. Samples were collected from ‘Laguna Chica’ lake in Catac (Ancash, Peru), between September 2023 and July 2024. Nostoc sphaericum formed spherical, brown–olive-green structures with a gelatinous consistency. Cyanobacterium was best developed with highest carbohydrate content (71.63% dw) in March. The optimal EPS extraction parameters were: water/sample ratio of 179.9:1, temperature of 88.6°C, and time of 190.6 min, yielding a product with 93.79% carbohydrates (dw). The FTIR spectrum confirmed characteristic functional groups of polysaccharides, while thermogravimetric (TGA) and calorimetric (DSC) analyses indicated high thermal stability of the extracted EPS. Functional properties related to hydration, emulsification, foaming, and gelation were subsequently evaluated to assess its performance at the material level. The results provide a systematic description of the extraction behaviour and functional attributes of Nostoc sphaericum EPS, establishing a physicochemical and functional baseline that supports further investigation of its applicability and future evaluation of process efficiency, scalability, and sustainability.

Instituciones: Universidad Nacional Agraria La Molina