Pilot scale production, structural characterization, and cytotoxicity assessment of insoluble linear β-1,3 glucan...

β-glucan is a valuable polysaccharide that has garnered attention for its nutraceutical and diverse biological applications. The present study involved the pilot-scale cultivation of Euglena gracilis, followed by β-glucan extraction, purification, characterization, and cytotoxicity assessment. The extracted β-glucan has a white, granular, discoidal shape with an erythrocyte-like appearance, and an average particle size of 3.15 ± 2.11 μm. The presence of β-linkage was evident from the occurrence of a band at 889.07 in the IR spectra. UV-Visible spectroscopy and the Congo red test showed that the extracted β-glucan is pure with a triple-helical structure. XRD spectra revealed the crystalline nature with clear peaks and varying amorphous content. The extracted β-glucan is linear, with β-1,3 linkages, and has a molecular weight of 480-500 kDa, as indicated by HPLC, NMR (¹H, ¹³C, COSY, HMBC, HMQC) GC-MS, and MALDI-TOF spectra. The MTT, Neutral Red Uptake (NRU), and Alamar Blue-based cytotoxicity studies on L929 (mouse fibroblast) cell line showed that the extracted β-glucan is safe and biologically non-toxic at concentrations up to 50 mg/mL. The present study established a basis for the production and extraction of β-glucan from microalgae at pilot scale, presenting opportunities for the commercialization of this important nutraceutical compound.