Fungi under Modified Atmosphere-The Effects of CO 2 Stress on Cell Membranes and Description of New Yeast Stenotrophomyces fumitolerans gen. nov., sp. nov.

High levels of carbon dioxide are known to inhibit the growth of microorganisms. A total of twenty strains of filamentous fungi and yeasts were isolated from habitats with enriched carbon dioxide concentration. Most strains were derived from modified atmosphere packed (MAP) food products or mofettes and were cultivated under an atmosphere of 20% CO ₂ and 80% O ₂ . The influence of CO ₂ on fungal cell membrane fatty acid profiles was examined in this study. Major changes were the increase in linolenic acid (C _18:3 cis 9, 12, 15) and, additionally in most strains, linoleic acid (C _18:2 cis 9, 12) with a maximum of 24.8%, at the expense of oleic (C _18:1 cis 9), palmitic (C _16:0 ), palmitoleic (C _16:1 cis 9) and stearic acid (C _18:0 ). The degree of fatty acid unsaturation increased for all of the strains in the study, which consequently led to lower melting temperatures of the cell membranes after incubation with elevated levels of CO ₂ , indicating fluidization of the membrane and a potential membrane malfunction. Growth was reduced in 18 out of 20 strains in laboratory experiments and a change in pigmentation was observed in several strains. Two of the isolated strains, strain WT5 and strain WR1, were found to represent a hitherto undescribed yeast for which the new genus and species Stenotrophomyces fumitolerans (MB# 849906) is proposed.