To achieve consecutive conversion from creatinine to urea and sarcosine using creatininase and creatinase encapsulated in spores of Saccharomyces cerevisiae.Creatininase encapsulated into the spore wall was produced and its specific activity was 3.4 ± 0.4 U/mg. By deletion of OSW2 gene, which causes a mild spore wall defect, the activity was increased to 10.9 ± 0.5 U/mg. Compared with soluble enzymes, spore-encapsulated creatininase was tolerant to environmental stresses; creatininase encapsulated in osw2∆ spores retained more than 90 % of the activity after treatment by SDS or proteinase K. Creatinase capsules could also be produced through spore encapsulation. The mixture of spores containing either creatininase or creatinase could mediate a two-step reaction to produce urea from creatinine; 5 mg spores produced 19 µmol urea in 10 min. Spores co-expressing creatininase and creatinase could also mediate the reactions more efficiently than the mixture of spores individually expressing each enzyme; the yield in 10 min was 38 µmol.Yeast spores can hold creatininase and creatinase simultaneously and catalyze the consecutive reactions.

l-Rhamnulose-1-phosphate aldolase from a thermophilic source (Thermotoga maritima MSB8) (RhaDT.mari) was heterologously overexpressed in Escherichia coli and the stereoselectivity of this enzyme with or without Nus tag was investigated. We also applied this enzyme to the synthesis of rare sugars d-psicose, d-sorbose, l-tagatose and l-fructose using our one-pot four-enzyme system. To the best of our knowledge, this is the first use of RhaD from a thermophilic source for rare sugar synthesis and the temperature tolerance of this enzyme paves the path for large scale fermentation.

Glycerol phosphate oxidase from Streptococcus pneumoniae (GPOS.pne) was purified and characterized. By the actions of GPOS.pne and dihydroxyacetone phosphate (DHAP)-dependent aldolases, various ketoses including rare sugars were synthesized with glyceraldehydes as acceptors in a one-pot four-enzyme system.

Saccharomyces cerevisiae spores are dormant cells, which can tolerate various types of environmental stress. In our previous work, we successfully developed biological and chemical methods for enzyme immobilization based on the structures of S. cerevisiae spore wall. In this study, we employed biological and chemical approaches for the immobilization of d-xylose isomerase (XI) from Thermus thermophilus and d-psicose 3-epimerase (DPEase) from Agrobacterium tumefaciens with yeast spores, respectively. The enzymatic properties of both immobilized XI and DPEase were characterized and the immobilized enzymes exhibit higher thermostability, broader pH tolerance, and good repeatability compared with free enzymes. Furthermore, we established a two-step approach for the bioconversion of d-glucose to d-psicose using immobilized enzymes. To improve the conversion yield, a multi-pot strategy was adopted for d-psicose production by repeating the two-step process continually. As a result, the yield of d-psicose was obviously improved and the highest yield reached about 12.0 %.