Kinetic model of lipase-catalyzed conversion of ascorbic acid and oleic acid to liposoluble vitamin C ester

Alginate-coated pomelo pith cellulose matrix for probiotic encapsulation and controlled release

A novel carrier comprised of ethanol- and alkali-modified cellulosic pomelo pith matrix coated with alginate was developed to improve viability while enabling gastrointestinal release of probiotics. Scanning electron microscopy imaging revealed the agricultural byproduct had a honeycomb-structured cellulose framework, enabling high loading capacity of the probiotic Lactobacillus plantarum up to 9 log CFU/g. Ethanol treatment opened up pores with an average diameter of 97 μm, while alkali treatment increased swelling and porosity, with an average pore size of 51 μm. The survival rate through the stomach was increased from 89.76 % to 91.08 % and 91.24 % after ethanol and alkali modification, respectively. The control group displayed minimal release in the first 4 h followed by a burst release. Both ethanol modification and alkali modification resulted in constant linear release over time. The release time was prolonged when decreasing the width of the pomelo peel rolls from 10 mm to 5 mm while keeping the volume of the peel constant. After 8 weeks of refrigerated storage, the cellulose-encapsulated probiotics retained viability above 7 log CFU/g. This study demonstrates the potential of the structurally intact, sustainably-sourced cellulosic pomelo pith for probiotic encapsulation and controlled delivery.

Controlled Nutrient Delivery through a pH-Responsive Wood Vehicle

To lower the risk of disease and improve health, many nutrients benefit from intestinal-targeted delivery. Here, we present a nutrient-delivery system based on a pH-responsive "wood scroll", in which nutrients are stored, protected, and controllably released through the rolled structure and natural microchannels of a flexible wood substrate, thus ensuring higher bioactivity as well as prolonged steady release of the nutrient load to the intestine. We loaded the wood's natural microchannels with probiotics as a proof-of-concept demonstration. The probiotic-loaded wood scrolls can survive the simulated conditions of the stomach with a high survival rate (95.40%) and exhibit prolonged release (8 h) of the probiotic load at a constant release rate (4.17 × 10⁸ CFUs/h) in the simulated conditions of the intestine. Moreover, by modifying the macroscopic geometry and microstructures of the wood scrolls, both the nutrient loading and release behaviors can be tuned over a wide range for customized or personalized nutrient management. The wood scrolls can also deliver other types of nutrients, as we demonstrate for tea polyphenols and rapeseed oil. This wood scroll design illustrates a promising structurally controlled strategy for the delivery of enteric nutrients using readily available, low-cost, and biocompatible biomass materials that have a naturally porous structure for nutrient storage, protection, and controlled release.

Industrial biotransformations catalyzed by microbial lipases: screening platform and commercial aspects

The successfulness of a lipase-catalyzed industrial process depends on a proper lipase selection. In this work, an alternative screening platform for industrially important biotransformations catalyzed by microbial lipases was proposed. Thus, the reactivity of sixty lipase activities from spore-forming microorganisms towards hydrolytic and transesterification reactions by using p-nitrophenyl palmitate as a chromogenic acyl donor substrate was explored. Only three biocatalysts were capable of catalyzing all reactions tested. Fourteen biocatalysts did not show hydrolytic activity at all; however, they displayed transesterification activities using ethanol, starch, low-methoxyl (LM) pectin, high-methoxyl (HM) pectin, or vitamin C as acyl acceptors. Using heat-treated biocatalysts, hydrolytic activities were not highly correlated with the corresponding transesterification activities using ethanol (r =  -0.058, p = 0.660), starch (r = 0.431, p = 0.001), LM pectin (r =  -0.010, p = 0.938), HM pectin (r = 0.167, p = 0.202), and vitamin C (r =  -0.048, p = 0.716) as acyl acceptor. In addition, to the best of our knowledge, several transesterification activities produced from microorganisms of the genus Bacillus, Brevibacillus, Lysinibacillus, Geobacillus, or Sporosarcina were reported for first time. Finally, the global lipase market was presented and segmented by date, application, geography and player highlighting the commercial contribution of microbial lipases.

Synthesis with Immobilized Lipases and Downstream Processing of Ascorbyl Palmitate

Ascorbyl palmitate is a fatty acid ester endowed with antioxidant properties, used as a food additive and cosmetic ingredient, which is presently produced by chemical synthesis. Ascorbyl palmitate was synthesized from ascorbic acid and palmitic acid with a Pseudomonas stutzeri lipase immobilized on octyl silica, and also with the commercial immobilized lipase Novozym 435. The latter was selected for optimizing the reaction conditions because of its high reactivity and stability in the solvent 2-methyl-2-butanol used as reaction medium. The reaction of the synthesis was studied considering temperature and molar ratio of substrates as variables and synthesis yield as response parameter. The highest yield in the synthesis of ascorbyl palmitate was 81%, obtained at 55 °C and an ascorbic acid to palmitic acid molar ratio of 1:8, both variables having a strong effect on yield. The synthesized ascorbyl palmitate was purified to 94.4%, with a purification yield of 84.2%. The use of generally recognized as safe (GRAS) certified solvents with a polarity suitable for the solubilization of the compounds made the process a viable alternative for the synthesis and downstream processing of ascorbyl palmitate.

Process optimization and kinetic evaluation for biosynthesis of D-isoascorbyl stearate

The synthesis of D-isoascorbyl stearate from D-isoascorbic acid and stearic acid with immobilized lipase (Novozym(®)435) as catalyst was studied. Response surface methodology and Box-Behnken design with six variables and three levels were employed to evaluate the effects of processing conditions on the conversion of D-isoascorbic acid. The results confirmed that the response surface method and statistical analysis were proved to be useful in developing optimal conditions for D-isoascorbyl stearate synthesis. The optimum conditions were predicted as follows: reaction temperature 48 °C, reaction time 17.7 h, immobilized lipase amount 50.0 % (w/w, of D-isoascorbic acid), substrate molar ratio 9:1 (stearic acid to D-isoascorbic acid), D-isoascorbic acid concentration 0.14 mol/L (based on solvent), 4A molecular sieve addition 200 g/L (based on solvent), and the optimal conversion was 90.6 %. Through the kinetics model fitting of the esterification, it was considered that the esterification conformed to a Ping-Pong bi-bi kinetic model with D-isoascorbic acid inhibition, and the obtained kinetic constants showed that the inhibition of D-isoascorbic acid and the enzyme affinity to substrate were abate with the increase of the reaction temperature.

Catalyzed ester synthesis using Candida rugosa lipase entrapped by poly(N-isopropylacrylamide-co-itaconic acid) hydrogel

This study reports the synthesis of polymeric matrices based on N-isopropylacrylamide and itaconic acid and its application for immobilization of lipase from Candida rugosa. The lipase was immobilized by entrapment method. Free and immobilized lipase activities, pH and temperature optima, and storage stability were investigated. The optimum temperature for free and entrapped lipase was found to be 40 and 45°C, while the optimum pH was observed at pH 7 and 8, respectively. Both hydrolytic activity in an aqueous medium and esterolytic activity in an organic medium have been evaluated. Maximum reaction rate (V_max) and Michaelis-Menten constants (K_m) were also determined for immobilized lipase. Storage stability of lipase was increased as a result of immobilization process. Furthermore, the operational stability and reusability of the immobilized lipase in esterification reaction have been studied, and it was observed that after 10 cycles, the residual activity for entrapped lipase was as high as 50%, implying that the developed hydrogel and immobilized system could provide a promising solution for the flavor ester synthesis at the industrial scale.

D-isoascorbyl palmitate: lipase-catalyzed synthesis, structural characterization and process optimization using response surface methodology

Background

Isoascorbic acid is a stereoisomer of L-ascorbic acid, and widely used as a food antioxidant. However, its highly hydrophilic behavior prevents its application in cosmetics or fats and oils-based foods. To overcome this problem, D-isoascorbyl palmitate was synthesized in the present study for improving the isoascorbic acid’s oil solubility with an immobilized lipase in organic media. The structural information of synthesized product was clarified using LC-ESI-MS, FT-IR, ¹H and ¹³C NMR analysis, and process parameters for high yield of D-isoascorbyl palmitate were optimized by using One–factor-at-a-time experiments and response surface methodology (RSM).

Results

The synthesized product had the purity of 95% and its structural characteristics were confirmed as isoascorbyl palmitate by LC-ESI-MS, FT-IR, ¹H, and ¹³C NMR analysis. Results from “one–factor-at-a-time” experiments indicated that the enzyme load, reaction temperature and D-isoascorbic-to-palmitic acid molar ratio had a significant effect on the D-isoascorbyl palmitate conversion rate. 95.32% of conversion rate was obtained by using response surface methodology (RSM) under the the optimized condition: enzyme load of 20% (w/w), reaction temperature of 53°C and D- isoascorbic-to-palmitic acid molar ratio of 1:4 when the reaction parameters were set as: acetone 20 mL, 40 g/L of molecular sieves content, 200 rpm speed for 24-h reaction time.

Conclusion

The findings of this study can become a reference for developing industrial processes for the preparation of isoascorbic acid ester, which might be used in food additives, cosmetic formulations and for the synthesis of other isoascorbic acid derivatives.