THE APPLICATION OF VARIOUS PROTIC ACIDS IN THE EXTRACTION OF (1-]3)-BETA-D-GLUCAN FROM SACCHAROMYCES-CEREVISIAE

Glucans are(1 --> 3)-beta-linked glucose polymers which have immune-st imulating capability. The extraction of water-insoluble (1 --> 3)-beta -D-glucan form Saccharomyces cerevisiae em ploys hydrochloric acid, Hy drochloric acid is difficult to employ in the large-scale pharmaceutic al extraction of glucans due to its corrosive nature and toxicity. To address these concerns, we determined whether acetic, formic or phosph oric acid can be substituted for hydrochloric acid in the process for the isolation of (1 --> 3)-beta-D-glucan. The resulting microparticula te glucans were employed as the starting material for the production o f (1 --> 3)-beta-D-glucan phosphate. C-13 NMR analysis of the glucan p hosphates derived from the acetic, formic or phosphoric acid-extracted microparticulate glucan show excellent correspondence to hydrochloric acid extracted glucan and laminarin, a (1 --> 3)-beta-D-glucan standa rd, indicating that the primary structure is not altered by the acid u sed for extraction. Glucan phosphate prepared from hydrochloric acid h ad a M-w of 7.2 x 10(4) g/mol, rms(z) of 17.7 nm, of 1.50 and (eta) of 49.0 mL/g. Glucan phosphate prepared from acetic acid had a primary p olymer peak with a M-w of 1.4 x 10(6) g/mol, rms(z) of 23.6 nm, I of 1 .93 and (eta) of 62.4 mL/g. Glucan phosphate prepared from formic acid had a main polymer peak with a M-w of 1.2 x 10(6) g/mol, rms(z) 27.1 nm, I of 1.56 and (eta) of 89.0 mL/g. Glucan phosphate prepared from p hosphoric acid had a primary polymer peak with a M-w of 6.6 x 10(5) g/ mol, rms(z) of 32.3 nm, I of 2.70 and (eta) of 91.3 mL/g. These data i ndicate that the molecular mass, size, polydispersity and intrinsic vi scosity of the glucan phosphate obtained is influenced by the pK(a) of protic acid employed to extract the microparticulate glucan. However, the primary structure and side-chain branching are not substantially altered regardless of the acid employed. (C) 1997 Elsevier Science Ltd .