NMR assignment of the galactomannan of Candida lipolytica

Comparative Analysis of Mannans Extraction Processes from Spent Yeast Saccharomyces cerevisiae

Mannans are outstanding polysaccharides that have gained exponential interest over the years. These polysaccharides may be extracted from the cell wall of Saccharomyces cerevisiae, and recovered from the brewing or synthetic biology industries, among others. In this work, several extraction processes-physical, chemical and enzymatic-were studied, all aiming to obtain mannans from spent yeast S. cerevisiae. Their performance was evaluated in terms of yield, mannose content and cost. The resultant extracts were characterized in terms of their structure (FT-IR, PXRD and SEM), physicochemical properties (color, molecular weight distribution, sugars, protein, ash and water content) and thermal stability (DSC). The biological properties were assessed through the screening of prebiotic activity in Lactobacillus plantarum and Bifidobacterium animalis. The highest yield (58.82%) was achieved by using an alkaline thermal process, though the correspondent mannose content was low. The extract obtained by autolysis followed by a hydrothermal step resulted in the highest mannose content (59.19%). On the other hand, the extract obtained through the enzymatic hydrolysis displayed the highest prebiotic activity. This comparative study is expected to lay the scientific foundation for the obtention of well-characterized mannans from yeast, which will pave the way for their application in various fields.

Isolation, Physicochemical Characterization, Labeling, and Biological Evaluation of Mannans and Glucans

The cell wall contains mannans and glucans that are recognized by the host immune system. In this chapter, we will describe the methods to isolate mannans and glucans from the C. albicans cell wall. In addition, we describe how to determine purity, molecular size, and structure of the mannans and glucans. We also detail how to prepare the carbohydrates for in vitro, ex vivo, or in vivo use by describing endotoxin removal (depyrogenation), derivatization, and labeling and evaluation of bioactivity.

Mannans and mannan oligosaccharides (MOS) from Saccharomyces cerevisiae - A sustainable source of functional ingredients

Sustainable industry practices and circular economy concepts encourage the transformation of production waste into by-products. Saccharomyces cerevisiae is widely used in fermentation industry worldwide, generating large amounts of spent yeast which is mainly directed to animal feed or discarded as waste. Instead of becoming and environmental problem, spent yeast can be directed to the extraction of valuable compounds such as mannans and mannan oligosaccharides (MOS). This review presents a compilation of the studies up to date regarding the different chemical, enzymatic, mechanical or physical processes addressed for mannans extraction and MOS production. Additionally, the existing studies on the chemical modification of mannans aimed to improve specific characteristics are also discussed. Finally, the more relevant bioactivities and potential applications of mannans, MOS and mannose are presented, together with products on the market containing these compounds.

Mannan structural complexity is decreased when Candida albicans is cultivated in blood or serum at physiological temperature

The Candida albicans cell wall provides an architecture that allows for the organism to survive environmental stress as well as interaction with host tissues. Previous work has focused on growing C. albicans on media such as Sabouraud or YPD at 30°C. Because C. albicans normally colonizes a host, we hypothesized that cultivation on blood or serum at 37°C would result in structural changes in cell wall mannan. C. albicans SC5314 was inoculated onto YPD, 5% blood, or 5% serum agar media three successive times at 30°C and 37°C, then cultivated overnight at 30°C in YPD. The mannan was extracted and characterized using 1D and 2D (1)H NMR techniques. At 30°C cells grown in blood and serum contain less acid-stable terminal β-(1→2)-linked d-mannose and α-(1→2)-linked d-mannose-containing side chains, while the acid-labile side chains of mannan grown in blood and serum contain fewer β-Man-(1→2)-α-Man-(1→ side chains. The decrement in acid-stable mannan side chains is greater at 37°C than at 30°C. Cells grown on blood at 37°C show fewer →6)-α-Man-(1→ structural motifs in the acid-stable polymer backbone. The data indicate that C. albicans, grown on media containing host-derived components, produces less complex mannan. This is accentuated when the cells are cultured at 37°C. This study demonstrates that the C. albicans cell wall is a dynamic and adaptive organelle, which alters its structural phenotype in response to growth in host-derived media at physiological temperature.

The Saccharomyces cerevisiae protein Mnn10p/Bed1p is a subunit of a Golgi mannosyltransferase complex

In the yeast Saccharomyces cerevisiae many of the N-linked glycans on cell wall and periplasmic proteins are modified by the addition of mannan, a large mannose-containing polysaccharide. Mannan comprises a backbone of approximately 50 alpha-1,6-linked mannoses to which are attached many branches consisting of alpha-1,2-linked and alpha-1,3-linked mannoses. The initiation and subsequent elongation of the mannan backbone is performed by two complexes of proteins in the cis Golgi. In this study we show that the product of the MNN10/BED1 gene is a component of one of these complexes, that which elongates the backbone. Analysis of interactions between the proteins in this complex shows that Mnn10p, and four previously characterized proteins (Anp1p, Mnn9p, Mnn11p, and Hoc1p) are indeed all components of the same large structure. Deletion of either Mnn10p, or its homologue Mnn11p, results in defects in mannan synthesis in vivo, and analysis of the enzymatic activity of the complexes isolated from mutant strains suggests that Mnn10p and Mnn11p are responsible for the majority of the alpha-1, 6-polymerizing activity of the complex.

Overview of N- and O-linked oligosaccharide structures found in various yeast species

Yeast and most higher eukaryotes utilize an evolutionarily conserved N-linked oligosaccharide biosynthetic pathway that involves the formation of a Glc3Man9GlcNAc2-PP-dolichol lipid-linked precursor, the glycan portion of which is co-translationally transferred in the endoplasmic reticulum (ER) to suitable Asn residues on nascent polypeptides. Subsequently, ER processing glycohydrolases remove the three glucoses and, with the exception of Schizosaccharomyces pombe, a single, specific mannose residue. Processing sugar transferases in the Golgi lead to the formation of core-sized structures (Hex<15GlcNac2) as well as cores with an extended poly-alpha1,6-Man 'backbone' that is derivatized with various carbohydrate side chains in a species-specific manner (Hex50-200GlnNAc2). In some cases these are short alpha1,2-linked Man chains with (Saccharomyces cerevisiae) or without (Pichia pastoris) alpha1,3-Man caps, while in other yeast (S. pombe), the side chains are alpha1,2-linked Gal, some of which are capped with beta-1,3-linked pyruvylated Gal residues. Charged groups are also found in S. cerevisiae and P. pastoris N-glycans in the form of mannose phosphate diesters. Some pathogenic yeast (Candida albicans) add poly-beta1,2-Man extension through a phosphate diester to their N-glycans, which appears involved in virulence. O-Linked glycan synthesis in yeast, unlike in animal cells where it is initiated in the Golgi using nucleotide sugars, begins in the ER by addition of a single mannose from Man-P-dolichol to selected Ser/Thr residues in newly made proteins. Once transported to the Golgi, sugar transferases add one (C. albicans) or more (P. pastoris) alpha1,2-linked mannose that may be capped with one or two alpha1,3-linked mannoses (S. cerevisiae). S. pombe is somewhat unique in that it synthesizes a family of mixed O-glycans with additional alpha1,2-linked Man and alpha1,2- and 1, 3-linked Gal residues.