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Production of ascorbic acid glucoside by alginate-entrapped mycelia of Aspergillus niger
Hsin-Ju Hsieh1, Kai-Yu Tung, Giridhar R Nair
1Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan.
Abstract:
The mycelia of Aspergillus niger, cultivated in a medium containing 45 g l(-1) maltose, 66 g l(-1) yeast extract, and 5 g l(-1) K(2)HPO(4) at 30 degrees C and 200 rpm, were used as a biocatalyst in the glucosylation of ascorbic acid. Free mycelia from 3-day-old culture, when used in a 6-h reaction with maltose as the acyl donor, gave 16.07 g l(-1) ascorbic acid glucoside corresponding to a volumetric productivity of 2.68 g l(-1) h(-1) and a conversion of 67%. Mycelia from 3-day-old cultures were entrapped in calcium alginate beads and used as a catalyst in the glucosylation of ascorbic acid. An ascorbic acid-to-maltose molar ratio of 1:9 was found to be optimum, and the conversion reached 75% after 12 h. The concentration of ascorbic acid glucoside produced at this molar ratio was 17.95 g l(-1), and the productivity was 1.5 g l(-1) h(-1). The biocatalyst was repeatedly used in a fixed bed bioreactor for the synthesis of ascorbic acid glucoside and approximately 17 g l(-1) of ascorbic acid glucoside corresponding to a volumetric productivity of 1.42 g l(-1) h(-1) was produced in each use. The conversion was retained at 70% in each use. The entrapped mycelia also exhibited exceptionally high reusability and storage stability. The product was purified to 85% by anion exchange and gel permeation chromatography with a final yield of 75%.
Insights
Aspergillus niger mycelia efficiently produce ascorbic acid glucoside using maltose. Entrapped mycelia offer high reusability and stability for biocatalysis, yielding a purified product.
Area of Science:
- Biotechnology
- Enzyme Catalysis
- Microbial Biotransformation
Background:
- Ascorbic acid (Vitamin C) is a vital nutrient with limited stability.
- Glucosylation enhances ascorbic acid's stability and bioavailability.
- Developing efficient biocatalytic methods for ascorbic acid glucosylation is crucial.
Purpose of the Study:
- To investigate Aspergillus niger mycelia as a biocatalyst for ascorbic acid glucosylation.
- To optimize reaction conditions for enhanced ascorbic acid glucoside production.
- To evaluate the reusability and stability of the biocatalyst.
Main Methods:
- Cultivation of Aspergillus niger mycelia.
- Glucosylation of ascorbic acid using free and immobilized mycelia with maltose as acyl donor.
- Optimization of molar ratio and reaction time.
- Repeated use of immobilized biocatalyst in a fixed-bed bioreactor.
- Product purification using chromatography.
Main Results:
- Free mycelia achieved 67% conversion yielding 16.07 g/L ascorbic acid glucoside in 6 hours.
- Immobilized mycelia in calcium alginate beads reached 75% conversion (17.95 g/L) at a 1:9 ascorbic acid-to-maltose ratio.
- The immobilized biocatalyst demonstrated high reusability (approx. 17 g/L per use) and retained 70% conversion over multiple cycles.
- Purification yielded 85% pure ascorbic acid glucoside with a 75% final yield.
Conclusions:
- Aspergillus niger mycelia are effective biocatalysts for ascorbic acid glucosylation.
- Immobilization enhances biocatalyst performance, reusability, and stability.
- This method offers a promising route for stable ascorbic acid derivative production.
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