Enzymatic synthesis of maltooligosaccharides is hampered due to lack of stability of soluble enzyme. This limitation can be tackled by cross linked enzyme aggregates (CLEAs) immobilization approach. However, substrate diffusion is a major bottleneck in cross linking technology. Herein, CLEAs of maltogenic amylase from Bacillus lehensis G1 (Mag1) was developed with addition of porous agent (Mag1-p-CLEAs). Comparison of thermal, pH and kinetic analysis with CLEAs without porous agent (Mag1-CLEAs) and free Mag1 was performed. Mag1-p-CLEAs with porous structure prepared at 0.8% (w/v) of citrus pectin (porous agent), 0.25% (w/v) of chitosan (cross linker) and cross linked for 1.5 h yielded 91.20% activity. 80% of activity is retained after 30 min of incubation at 40 °C and showed longer half-life than free Mag1 and Mag1-CLEAs. Mag1-p-CLEAs also showed pH stability at acidic and alkaline pH. The 1.68-fold increase in Vmax value in comparison to Mag1-CLEAs showed that the presence of pores of Mag1-p-CLEAs enhanced the beta-cyclodextrin accessibility. The increase in high catalytic efficiency (Kcat/Km) value, 1.90-fold and 1.05-fold showed that it also has better catalytic efficiency than free Mag1 and Mag1-CLEAs, respectively. Mag1-p-CLEAs not only improved substrate diffusibility of CLEAs, but also leads to higher thermal and pH stability of Mag1.
Maltooligosaccharides (MOSs) are emerging oligosaccharides in food-based applications and can be synthesized through the enzymatic synthesis of maltogenic amylase from Bacillus lehensis G1 (Mag1). However, the lack of enzyme stability makes this approach unrealistic for industrial applications. The formation of cross-linked enzyme aggregates (CLEAs) is a promising tool for improving enzyme stability, and the substrate accessibility problem of CLEA formation was overcome by the addition of porous agents to generate porous CLEAs (p-CLEAs). However, p-CLEAs exhibited high enzyme leaching and low solvent tolerance. To address these problems, p-CLEAs of Mag1 (Mag1-p-CLEAs) were entrapped in calcium alginate beads (CA). Mag1-p-CLEAs-CA prepared with 2.5% (w/v) sodium alginate and 0.6% (w/v) calcium chloride yielded 53.16% (17.0 U/mg) activity and showed a lower deactivation rate and longer half-life than those of entrapped free Mag1 (Mag1-CA) and entrapped non-porous Mag1-CLEAs (Mag1-CLEAs-CA). Moreover, Mag1-p-CLEAs-CA exhibited low enzyme leaching and high tolerance in various solvents compared to Mag1-p-CLEAs. A kinetic study revealed that Mag1-p-CLEAs-CA exhibited relatively high affinity towards beta-cyclodextrin (β-CD) (Km = 0.62 mM). MOSs (300 mg/g) were synthesized by Mag1-p-CLEAs-CA at 50 °C. Finally, the reusability of Mag1-p-CLEAs-CA makes them as a potential biocatalyst for the continuous synthesis of MOSs.
Constitutive androstane receptor (CAR) encoded by the nuclear receptor subfamily 1, group I, member 3 (NR1I3) gene regulates the elimination of bilirubin through activating the components of the bilirubin clearance pathway. Hence, NR1I3 genetic variants may affect bilirubin metabolism and result in neonatal hyperbilirubinemia. Thus far, research which investigates the association between NR1I3 variants and neonatal hyperbilirubinemia has not been undertaken in any population. The present study aimed to evaluate the influence of MPJ6_1I3008 (rs10157822), IVS8+116T>G (rs4073054) and 540A>G (rs2307424) on neonatal hyperbilirubinemia development in the Malay population. Buccal swabs were collected from 232 hyperbilirubinemia and 277 control term newborns with gestational age ≥37weeks and birth weight ≥2500g. The NR1I3 variants were genotyped by using high resolution melting (HRM) assays and verified by DNA sequencing. Gender, mode of delivery and birth weight did not differ between hyperbilirubinemia and control groups. The genotypic and allelic frequencies of MPJ6_1I3008, IVS8+116T>G and 540A>G were not significantly different between the groups. However, stratification by gender revealed a significant inverse association between homozygous variant genotype of MPJ6_1I3008 and risk of neonatal hyperbilirubinemia in the females (OR, 0.44; 95% CI, 0.20-0.95; p=0.034). This study demonstrates that the homozygous variant genotype of MPJ6_1I3008 was associated with a significant reduced risk of neonatal hyperbilirubinemia in the females.