Coencapsulation of Oxygen Carriers and Glucose Oxidase in Polyelectrolyte Complex Capsules for the Enhancement of D-Gluconic Acid and δ-Gluconolactone Production

Figures & data

Figure 1. Chemical equation of glucose oxidation catalysed by glucose oxidase (GOD) and catalase (CAT), compiled according to [2].

Table 1. Viscosity of the PA solutions and statistical analysis of the size and membrane thickness of GOD-SA-CS/PMCG capsules with coencapsulated oxygen carriers: 4% (w/w) of poly(dimethylsiloxane) (PDMS), 10% (w/w) of n-dodecane (DOD) and 10% of perfluorodecaline (PFD), respectively

Sample	PA solution viscosity [mPa·s]	Average capsule size [mm]/SD	Average membrane thickness [mm]/SD
Reference*	337±25	0.77±0.02/3	0.10±0.01/10
PDMS	411±20	0.79±0.02/3	0.11±0.01/9
PDMS-DOD	234±18	0.73±0.03/4	NA/-
PDMS-PFD	98±10	0.74±0.04/5	0.07±0.01/14

^*GOD-SA-CS/PMCG capsules without oxygen carriers; NA – not available, since the membrane could not be seen, SD – standard deviation expressed in [%].

Figure 2. Representative images of GOD-SA-CS/PMCG microcapsules: a) reference sample without oxygen carriers; b) capsules with an emulsion of PDMS 4% (w/w) and PFD 10% (w/w); c) capsules with PDMS 4% (w/w); d) capsules with an emulsion of PDMS 4% (w/w) and DOD 10% (w/w). Digitized images were taken either by an optical microscope (a, c) or a stereomicroscope (b, d) equipped with a digital camera and interfaced to a PC.

Figure 3. Relative enzyme activities for GOD-SA-CS/PMCG capsules using different oxygen feeding conditions, including air (•) and pure oxygen (○), at different glucose concentrations. Oxygen concentrations in reaction mixtures, measured by an oximeter, were 0.25 mM using air and 0.625 mM using pure oxygen. GOD activities were measured spectrophotometrically. 100% activity = 21.1±1.1 U·g⁻¹.

Table 2. Comparison of enzyme activity (A) and space-time yield (STY) of the product (mixture of D-gluconic acid and δ-gluconolactone) for GOD-SA-CS/PMCG capsules with the following concentration of coencapsulated oxygen carriers: 4% (w/w) of poly(dimethylsiloxane) (PDMS), 10% (w/w) of n-dodecane (DOD) and 10% (w/w) of perfluorodecaline (PFD), respectively; oxygen concentration was kept at 0.625 mM

Preparative	A[U·g^−1]	STY[g·l^−1·day^−1]
Reference*	21.0 ± 1.1	44.3 ± 2.0
DOD-PDMS	38.4 ± 2.0	83.4 ± 3.4
PFD-PDMS	36.5 ± 1.5	79.6 ± 3.7
PDMS	35.2 ± 2.1	77.9 ± 3.1

*GOD-SA-CS/PMCG capsules without oxygen carriers.

Figure 4. Effect of coencapsulated oxygen carriers within the GOD-SA-CS/PMCG capsules expressed as the time evolution of the product (D-gluconic acid – δ-gluconolactone mixture) concentration during glucose oxidation. The oxygen carrier concentrations in PA solution were PDMS 4% (w/w), PFD 10% (w/w), DOD 10% (w/w). GOD-SA-CS/PMCG capsules formed in the absence of oxygen carriers were used as the reference. Product concentrations were determined by HPLC. Oxygen concentration was 0.625 mM.

Figure 5. Effect of coencapsulated oxygen carriers within the GOD-SA-CS/PMCG capsules expressed as the time evolution of the glucose concentration monitored on-line by flow microcalorimetry (FC) and sample analysis by HPLC. Depicted concentrations represent average values from measurements by FC and HPLC. The oxygen carrier concentrations in PA solution were PDMS 4% (w/w), PFD 10% (w/w), DOD 10% (w/w). GOD-SA-CS/PMCG capsules formed in the absence of oxygen carriers were used as reference. Oxygen concentration was 0.625 mM.

Figure 6. Dependence of enzyme activity on concentration of MnO₂ coencapsulated within the GOD-SA-CS/PMCG capsules. GOD activities were determined spectrophotometrically. Oxygen concentration was 0.625 mM.

Table

A	Enzyme activity [U·g^−1]
CAT	Catalase
CS	Cellulose sulfate
DOD	n-dodecane
GOD	Glucose oxidase
GOD-SA-CS/PMCG	Capsules prepared from sodium alginate, cellulose sulfate, poly(methylene-co-guanidine), CaCl2 and NaCl with immobilized glucose oxidase
PA	Polyanion aqueous solution prepared from sodium alginate, cellulose sulfate and NaCl
PC	Polycation aqueous solution prepared from poly(methylene-co-guanidine), CaCL and NaCl
PDMS	Poly(dimethylsiloxane)
PFD	Perfluorodecaline
PMCG	Poly(methylene-co-guanidine)
SA	Sodium alginate
SA-CS/PMCG	Capsules prepared from sodium alginate, cellulose sulfate, poly(methylene-co-guanidine), CaCl2 and NaCl
STY	Space-time yield of produet [g·l^−1·day^−1]

Vikartovská, A., Bučko, M., Mislovičová, D., Pätoprstý, V., Lacík, I., Gemeiner, P. (2007). Improvement of the stability of glucose oxidase via encapsulation in sodium alginate-cellulose sulfate-poly(methylene-co-guanidine) capsules. Enzyme and Microbial Technology 41:748–755.

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