FT-IR Method Limitations for β-Glucan Analysis

Abstract

β-glucans are known as biological response modifiers. However, different sources can result in structural differences and as a result differences in their biological activity. The hot water extraction method allows to obtain, high molecular weight β-glucans without altering their structure by using strong chemicals, such as alkalis or acids. Analysis of β-glucans by FT-IR and NMR spectroscopy in solid state is superior to analysis in solution as it allows researchers to study the preserved structure of the extracted polysaccharides. FT-IR spectroscopy was used in this study to make side-by-side comparison analysis of hot water extracted β-glucans from different yeast sources. NMR spectroscopy was used to confirm findings made by FT-IR spectroscopy. Extracted β-glucans exhibit characteristic structure of β-1,3/1,6-linked glucans with noticeable levels of proteins, possibly in a form of oligopeptides, chitin and other impurities. β-glucans obtained from C. guilliermondii, P. pastoris and S. pastorianus exhibited higher protein content. Differences in mannan, chitin and α-glucan content were also observed; however, the species-specific structure of obtained β-glucans could not be confirmed without additional studies. Structural analysis of high molecular weight β-glucans in solid state by FT-IR spectroscopy is difficult or limited due to band intensity changes and overlapping originating from different molecules.

Comparative Analysis of Mannans Extraction Processes from Spent Yeast Saccharomyces cerevisiae

“…All ATR-FT-IR spectra also exhibit a sharp band at 1647 cm −1 , which can be attributed to the C-O asymmetric stretching vibration [ 51 ]; a vibration band at 1025 cm −1 assigned to the O-H variable angle vibrations and the characteristic absorption of the mannan α-chain appeared at 814 cm −1 [ 13 , 50 ]. The spectra corresponding to the mannan extracts obtained by autolysis and enzymatic hydrolysis, ATL and EH, respectively, exhibit two strong vibrations at 2925 and 2854 cm −1 (lipid region) that can be assigned to the asymmetric and symmetric vibrational modes of CH 2 groups, respectively, and a sharp vibration at 1743 cm −1 can be attributed to the C=O stretching, generally representing lipids [ 52 ].…”

Solid-State 13C Nuclear Magnetic Resonance Study of Soluble and Insoluble β-Glucans Extracted from Candida lusitaniae

“…Signals from the aromatic region 120-140 ppm are inconclusive. Thus, the singular presence of a peak around 33 ppm could suggest the presence of specific non-aromatic amino acids [2,3,27,42]. However, the cross-connections between glucans, chitin and proteins must be established [25].…”

“…β-glucan extraction using hot water was carried out using the modified method originally described by Liu et al [50] and described in our previous work [42]. Briefly, cell wall preparations were suspended in distilled water and autoclaved at 121 • C for 4 h. After this, suspension was centrifuged at 5000× g for 10 min, the supernatant was discarded, cell walls were washed three times with distilled water and air-dried at 60 • C until dry.…”

M1 macrophages polarized by crude polysaccharides isolated from Auricularia polytricha exhibit anti-tumor effect on human breast cancer cells

“…The polysaccharides, the long-chain polymeric carbohydrates, exhibited vibration characteristics in the range of 1600-1700 cm −1 with C=O stretching. In addition, Band intensity at 1000-1200 cm −1 strongly indicated the presence of the β-glycosidic C-O bond 14 . The yeast 1,3:1,6 -β-D-glucan showed the specific band at 890 cm -1 at the anomeric region 15 .…”