Summary: Growth of the yeast IFP 206 in methanol- and glucose-containing media led respectively to very and weakly flocculent cells. Mannans from both kinds of cells were extracted and compared. Chemical analysis and molecular mass estimation showed some differences between the mannans from very and weakly flocculent cells, especially in quantitative amino acid content. H NMR analysis showed that both kinds of mannan contained α-1,2 and β-1,2 linkages. Two acetolysis conditions, combined with H NMR analysis, revealed that mannans from both kinds of cells were composed of mannose, mannobiose, mannotriose, mannotetraose and mannopentaose side-chains with the following respective structures: Man; Manα1.2Man; Manα1.2Manα1.2Man; Manβ1.2Manα1.2Man; Manβ1.2Manβ1.2Manα1.2Man; Manα1.2Manβ1.2Manβ1.2Manα1.2Man. Additionally the β-1,2 linkages of the non-reducing terminal residues of the mannotetraose were shown to be acetolysislabile. The mannans from very flocculent cells were richer in mannopentaose than the mannans from weakly flocculent cells. According to these results, the extended conformations in the branching moieties of the mannan could be the basis of the higher degree of flocculation of the methanol-grown cells.


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