The aim of this work is to investigate the influence of an inhibitor over free and microencapsulated enzymes. Microencapsulation is one of the techniques for enzyme immobilization, which is a very common process in the industry to stabilize enzymes and to increase the time and the range of applicability. There are several microencapsulation techniques, with different adaptations and specificities. In this work we used a spray drying method which is a technology used in industry due to its low cost, availability of equipment and efficiency. Spray drying is also a clean technology because it avoids the use of organic solvents during the encapsulation process. This study focused on the enzyme β-galactosidase, due to its importance in health and industry. Chitosan was selected as encapsulating agent considering all the advantages of this natural polymer. The microcapsules were prepared by spray drying and characterized by their particle size and surface morphology. Structural analysis of the surface of the particles was performed by Scanning Electron Microscopy (SEM). The SEM results show that the obtained microcapsules have a diameter smaller than 5 μm and a regular shape. The activity of the enzyme was studied by a spectrophotometric method using the substrate ONPG (O-Nitrophenyl-β,Dgalactopyranoside) and MGP (methyl-β,D-galactopyranosidase) as an inhibitor. It was concluded that there are differences on β-galactosidase activity in the presence of the inhibitor. The results also showed that the use of an encapsulating agent increases the diffusional effect of the released enzyme, and also reduces the initial activity of the enzyme.

No abstract

Recently, the studies about vitamin B12 increased due to the high number of people who can develop vitamin B12 deficiency, namely: vegetarians, pregnant women or with vitamin B12 malabsorption. One solution to correct the low nutritional intake of vitamin B12 can be using food supplements or pharmaceuticals, based on the vitamin B12 microencapsulation. In the present research, the vitamin B12 microencapsulation and the controlled release of fresh and 4 months' storage samples of vitamin B12 microcapsules were studied. The microcapsules were prepared using a spray-drying technique, and 7 biopolymers were used as encapsulating agents: arabic gum, sodium alginate, carrageenan, maltodextrin, modified starch, xanthan and pectin. The product yield of the spray-dryer ranged from 20 to 50%. The microparticles were also characterized in terms of size and morphology. The vitamin B12 release profiles from microcapsules were assessed by spectrophotometric analysis, at 361.4 nm, in deionized water at 22ºC and simulated gastric fluid at 37ºC. This study showed that the vitamin B12 microcapsules, with good stability properties, can be produced with several encapsulating agents and proved the possibility of releasing the vitamin in different periods of time.

Natural biopolymers have attracted the curiosity of the scientific community as matrixes for application in controlled release systems, especially in the food industry. Numerous active compounds have been encapsulated or incorporated in polymeric matrixes for food fortification, supplementation and preparation of nutraceutical products. The controlled release systems, namely the microencapsulated ones have become a challenging methodology to design new materials. The microencapsulated systems can be used to increase the effectiveness of many active compounds in industry, allowing the reformulation of a large number of products, improving and giving them better and new properties. In this chapter, the applicability of the controlled release systems in nutraceuticals products and functional foods using biopolymers as encapsulating agents is discussed. The main microencapsulation methods, the most relevant biopolymers used as wall materials, the controlled release mechanisms, and the models used to evaluate the release are presented. Finally, some potential applications of controlled delivery systems in food are discussed.

Molinate (S-ethyl-azepane-1-carbothioate) is a thiocarbamate herbicide used in rice cultivation for the control of grass weeds. Environmental contamination with molinate is of major concern due to the adverse effects described both for humans and animals. Molinate hydrolase, a novel amidohydrolase previously characterized, is responsible for the initial breakdown of molinate, cleaving the thioester bond of molinate, releasing ethanethiol and azepane-1-carboxylate (ACA). Biotechnology is the key for sustainable farming. With advances in biotechnology, bioremediation has become one of the most rapidly developing fields of environmental restoration. Through the microencapsulation of molinate hydrolase, we are aiming to develop a bioremediation process for the effective molinate degradation in rice paddies. The purpose of this work was to develop and validate an UV method to effectively quantify the substrate (molinate) in further assays with free and microencapsulated molinate hydrolase. The analytical method was validated and the main parameters, as limit of detection, linearity range, precision and accuracy were determined, and compared to those obtained by HPLC (regarding free enzyme kinetics). Both methods show to be linear (r > 0.999) over the concentration range of 0.005-0.150 mM molinate. The global uncertainty, estimated accordingly to the bottom-up approach used by Eurachem, was estimated for both methods. The UV analytical method is effective and seems that it can be applied in future for the quantification of molinate breakdown by free and encapsulated molinate hydrolase.