Product solubility control in cellooligosaccharide production by coupled cellobiose and cellodextrin phosphorylase.

ABSTRACT: Soluble cellodextrins (linear ?-1,4-d-gluco-oligosaccharides) have interesting applications as ingredients for human and animal nutrition. Their bottom-up synthesis from glucose is promising for bulk production, but to ensure a completely water-soluble product via degree of polymerization (DP) control (DP???6) is challenging. Here, we show biocatalytic production of cellodextrins with DP centered at 3 to 6 (~96?wt.% of total product) using coupled cellobiose and cellodextrin phosphorylase. The cascade reaction, wherein glucose was elongated sequentially from ?-d-glucose 1-phosphate (?Glc1-P), required optimization and control at two main points. First, kinetic and thermodynamic restrictions upon ?Glc1-P utilization (200?mM; 45°C, pH 7.0) were effectively overcome (53% ? ?90% conversion after 10?hrs of reaction) by in situ removal of the phosphate released via precipitation with Mg2+ . Second, the product DP was controlled by the molar ratio of glucose/?Glc1-P (?0.25; 50?mM glucose) used in the reaction. In optimized conversion, soluble cellodextrins in a total product concentration of 36?g/L were obtained through efficient utilization of the substrates used (glucose: 98%; ?Glc1-P: ?80%) after 1?hr of reaction. We also showed that, by keeping the glucose concentration low (i.e., 1-10?mM; 200?mM ?Glc1-P), the reaction was shifted completely towards insoluble product formation (DP ?9-10). In summary, this study provides the basis for an efficient and product DP-controlled biocatalytic synthesis of cellodextrins from expedient substrates.

SUBMITTER: Zhong C 

PROVIDER: S-EPMC6767486 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature