title: Applied usage of yeast spores as chitosan beads.
abstract: In this study, we present a nonhazardous biological method of producing chitosan beads using the budding yeast Saccharomyces cerevisiae. Yeast cells cultured under conditions of nutritional starvation cease vegetative growth and instead form spores. The spore wall has a multilaminar structure with the chitosan layer as the second outermost layer. Thus, removal of the outermost dityrosine layer by disruption of the DIT1 gene, which is required for dityrosine synthesis, leads to exposure of the chitosan layer at the spore surface. In this way, spores can be made to resemble chitosan beads. Chitosan has adsorptive features and can be used to remove heavy metals and negatively charged molecules from solution. Consistent with this practical application, we find that spores are capable of adsorbing heavy metals such as Cu(2+), Cr(3+), and Cd(2+), and removal of the dityrosine layer further improves the adsorption. Removal of the chitosan layer decreases the adsorption, indicating that chitosan works as an adsorbent in the spores. Besides heavy metals, spores can also adsorb a negatively charged cholesterol derivative, taurocholic acid. Furthermore, chitosan is amenable to chemical modifications, and, consistent with this property, dit1Δ spores can serve as a carrier for immobilization of enzymes. Given that yeast spores are a natural product, our results demonstrate that they, and especially dit1Δ mutants, can be used as chitosan beads and used for multiple purposes.
authors.affiliation: Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China.
authors.forename: Haini
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tachikawa
authors.affiliation: Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China xdgao@jiangnan.edu.cn hideki@jiangnan.edu.cn.
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Gao
authors.affiliation: Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China xdgao@jiangnan.edu.cn hideki@jiangnan.edu.cn.
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakanishi
mesh_terms: D000327:Adsorption; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D048271:Chitosan / Q000737:chemistry / Q000378:metabolism*; D019877:Hydroxymethyl and Formyl Transferases / Q000235:genetics / Q000378:metabolism; D019216:Metals, Heavy / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013172:Spores, Fungal / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D019216:Metals, Heavy; D029701:Saccharomyces cerevisiae Proteins; D048271:Chitosan; C503580:DIT1 protein, S cerevisiae; D019877:Hydroxymethyl and Formyl Transferases