[1S02m] 02. AFOB - Part 1

10:25 AM - 10:50 AM JST(1:25 AM - 1:50 AM UTC)

[1AFOB-02-KL] Enzymatic production of cellulose nanofibers using cellulases and expansins and its application to the preservation of avocados

○Joo-Hyun Seo¹, Kang-In Jeon¹, Minha Kim¹ (1. Kookmin University (Korea))

Keywords:

cellulose nanofiber,cellulase,expansin,fruit preservation,solubility prediction

Cellulose nanofibers (CNF) has wide industrial application potential. If CNF are made of food grade cellulose and food grade enzyme, those can be applied to food coating material for fruits, vegetables, meat and other food. CNF exhibits high moisture barrier properties and oxygen barrier properties to result in the quality preservation of food such as fruits. In this study, food grade cellulose was treated with food grade cellulases to produce CNF with the potential application to the preservation of avocados. Among the various food grade cellulases, Viscoflow MG, Viscozyme FG and Laminex Super 3G was selected based on the cellulose-degrading activity. For the industrial purpose, we investigated the reaction characteristics of mixture of three selected enzymes. The optimal conditions for the mixture of three enzymes were reaction temperature of 50 °C, a substrate-to-enzyme ratio of 5:1 and the addition of divalent cation Mn²⁺ at pH 5.0. Estimated kinetic constants of each enzyme and enzyme mixture were also investigated. Enzyme mixture showed higher V_max suggesting the suitability for high substrate concentration. Finally, after producing CNF using wheat cellulose and enzyme mixture, we applied CNF to avocados whether CNF coating lengthen the preservation period of avocado. The application of CNF derived from wheat cellulose to avocados showed significant maintenance of appearance and remarkable prevention from weight loss. To further improve the productivity of cellulase reaction, expansins having high soluble expression in Escherichia coli were searched using bioinformatics tools. Homologs of expansins were gathered and all the putative expansins were scored using SoluProt. The top two expansins (expansins from Bacillus sp. and B. mojavensis) in their SoluProt score exhibited high solubility when expressed in E. coli. When expansins were treated, B. sp. expansin and B. mojavensis exhibited 2.3- and 2.2-fold increased productivity, respectively. Furthermore, the endoglucanase fused with B. mojavensis expansin at its C-terminal, the fusion enzyme showed a 16% increase in activity in comparison with endoglucanase itself. It is expected that the protein engineering approaches employed in this study will result in the high applicability of CNF to food coatings.