Microencapsulation of glucosyltransferase by ionic gelation

CONTESINI, FJ; IBARGUREN, CAROLINA; AUDISIO, M. CARINA; SATO, H.H.; GROSSO, CARLOS RF

Irlanda

Conferencia; XVI International Conference on Bioencapsulation; 2008

Isomaltulose (Palatinose®) is a reducing sugar, isomer of sucrose, no toxic, with low cariogenic potential and produced by enzymatic conversion from sucrose by glucosyltransferase from few species such as Erwinia sp. D12. It is well known the use of enzyme immobilization techniques to produce stable and reusable biocatalysts. Within this framework, the microencapsulation by ionic gelation is straightforward and inexpensive and also adding hydrophobic materials can improve the retention of proteins during the immobilization process. In this work the microencapsulation of glucosyltranferase produced by the strain Erwinia sp. D12 was studied, using pectin of low esterification grade as wall material; as well as the influence of the addition of a mixture of butter milk and oleic acid in the retention process of the enzyme. The capsules contained 2% (w/v) of pectin, 5% (v/v) of glucosyltransferase and in the case of capsules with fat, 2% w/v of a mixture (1:1) (butter:oleic acid). The mixture was homogenized and hence sprayed on a solution of CaCl2 (2%, w/v) at 25°C. After a curing period of 30 minutes, the capsules were sieved (25µm), and then washed with distilled water. It was maintained at refrigerated conditions (wet capsules, WC) and also some amount of moist capsules was freeze dried (FDC). Moisture, protein content (Kjeldahl) and encapsulation efficiency was determined for WC, so as size distribution and morphology by optical microscopy, whereas in the FDC swelling and morphology by Scanning Electron Microscopy (SEM) was analyzed. Enzymatic activity of equivalent quantities of WC and FDC was determined using a solution of sucrose 10% (w/v) in distilled water as a substrate. After each batch of 30 minutes, the capsules were recovered from the reaction medium and reused in a new cycle. The protein encapsulation efficiency was slightly higher for the capsules with fat (55%) than for the capsules without fat (51%), and the moisture content was 97% and 94% respectively. All the capsules showed spherical shape, and multinucleated core distribution. The average size was about 196 ìm (microcapsules with fat) and 173 (microcapsules without fat). The capsules with fat maintained its size and largely spherical shape, as can be observed by SEM, while capsules without fat are much more brittle and crushed. The higher enzyme activity were obtained for wet capsules with fat, with retention of specified activity during the 1st 3 cycles of reaction (30 min), decreasing 60% of the activity in the 4th and 5th cycle and a 80%  in the 6th cycle. The activity of the enzyme in the freeze dried capsules was considerably lower, but concentrated non-encapsulated enzyme freeze dried showed lower activity.