Oxidoreductase (OXR) enzymes are in high demand for biocatalytic applications in food industry and cosmetics: glucose oxidase (GOx), cellobiose dehydrogenase (CBDH), bioremediation: horseradish peroxidase (HRP), laccase (LAC), and medicine for biosensors and miniature biofuel cells (GOx, CBDH, LAC, HRP). They can be used in a soluble form and/or within the yeast cell walls expressed as chimeras on the surface of yeast cells (YSD), such as P. pastoris and S. cerevisiae. However, most of the current studies suffer from either low yield for soluble enzyme expression or low enzyme activity when expressed as chimeric proteins using YSD. This is always the case in studies dealing with heterologous expression of oxidoreductase enzymes, since there is requirement not only for multiple OXR genes integrations into the yeast genome (super transformations), and codon optimization, but also very careful design of fermentation media composition, and fermentation conditions during expression due to need for adding transition metals (copper, iron), and metabolic precursors of FAD and heme. Therefore, scientists are still trying to find optimal formula using above mentioned approaches, and most recently also using protein engineering and directed evolution for additional increase in the yield of recombinant enzyme production. In this review article we will cover all the current state of the art technologies and most recent advances in the field that yielded high expression level for some of these enzymes in specially designed expression/fermentation systems. We will also tackle and discuss new possibilities for further increase in fermentation yield by the cutting-edge technologies such are directed evolution, protein and strain engineering, high-throughput screening methods based on in vitro compartmentalization, flow cytometry and microfluidics.

Alginate is naturally occurring polymer derived from brown algae biomass, which has found numerous applications in various fields. Chemical modification of alginate is widely used to improve the physicochemical properties of alginate and to provide new potential for various applications. In this article, we modified alginate with L-DOPA, using periodate oxidation and reductive amination, in order to be get more suitable biopolymer for biocatalysts immobilization and hydrogel formation. Obtained modified alginate was used for immobilization of laccase on cell walls. For this purpose, laccase from Streptomyces cyaneus was expressed on the surface of Saccharomyces cerevisiae EBY100 cells. Obtained cell wall laccase was immobilized within L-DOPA-alginate beads, by crosslinking of L-DOPA-alginate with calcium ions and laccase. The effect of additional crosslinking of beads by green light induced photopolymerization with eosin Y was investigated. The immobilized laccase systems were used for dye decolorization and also investigated in multiple treatment processes of dye decolorization. Beads with L-DOPA-alginate with higher degree of modification (5.0 mol%) showed higher enzymatic activity and better de-colorization efficiency compared to those with lower degree of modification (2.5 mol%). Obtained immobilized biocatalysts are suitable for the decolorization of dye Evans Blue due to their high efficiency and reusability.