Banca de DEFESA: WALESKA RAYANE DANTAS BEZERRA DE MEDEIROS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : WALESKA RAYANE DANTAS BEZERRA DE MEDEIROS
DATE: 30/03/2020
TIME: 14:00
LOCAL: Auditório do NUPEG (Centro de Tecnologia - UFRN)
TITLE:

Production, concentration and partial characterization of lipolytic enzymes of  Aspergillus niger in solid state fermentation

KEY WORDS:

Enzymatic activity. Experimental design. Agro-industrial residues.

PAGES: 110
BIG AREA: Ciências da Saúde
AREA: Farmácia
SUMMARY:

The lipases are enzymes with various applications in the food, pharmaceutical and cosmetic areas because of their versatility. The goals of the present study were to evaluate the production of Aspergillus niger IOC 4003 lipases by solid state fermentation using low cost substrates and to perform partial purification of the obtained lipases. The cultivation of A. niger was initially conducted using multivariate analysis. To select the variables with the greatest effect, Plackett-Burman (PB) experimental design was performed with 15 tests and 11 factors (cottonseed cake/wheat bran ratio, tilapia viscera oil concentration, cultivation time, pH, concentration of inoculum, moisture, glucose, urea, yeast extract, KH2PO4 and MgSO4). After a 23 Central Rotational Composite Design was carried out with the three most significant PB variables: cultivation time, cottonseed cake/wheat bran ratio and moisture. The response variable (lipolytic activity) was measured in the enzymatic extracts by spectrophotometry using p-nitrophenyl-palmitate. The results showed that the substrate combinations with the lowest percentage of cotton cake and the highest percentage of wheat bran and the extreme conditions of cultivation time and moisture contributed to the increase in enzymatic activity. The highest lipolytic activity (0.091 U/g) was obtained with 30% cotton cake, 50% moisture and 240 hours of cultivation. This condition was reproduced with supplementation of the inducers olive oil, tween 80 and triton X-100. However, there was no statistical difference with and without supplementation. The crude enzymatic extract was submitted to precipitation with acetone and ethanol. The best profiles were verified with the 40% acetone fraction (29.04% yield and purification factor 4.04) and the 20% ethanol fraction (42.47% yield and purification factor 5.03). The fractions 40% acetone and 20% ethanol showed predominance of a band with a molecular mass of 115 kDa, suggestive of the presence of lipases. The stability of the fraction containing pre-purified lipases was evaluated at pH 3 to 10 and at temperatures from 30 to 60 °C for 6 hours. The lowest stability occurred at pH 3 maintaining a residual lipolytic activity of 74.62%. The most important loss of activity was 15.10%, which occurred only at 60 °C. Therefore, from the cultivation of A. niger in solid state fermentation it was possible to obtain pre-purified lipases with good stability at temperatures and pHs, which can be of great interest in several industrial processes.

BANKING MEMBERS:
Externa ao Programa - 2378605 - CRISTIANE FERNANDES DE ASSIS
Externo ao Programa - 1346198 - EVERALDO SILVINO DOS SANTOS
Presidente - 3652554 - FRANCISCO CANINDE DE SOUSA JUNIOR
Externo à Instituição - SÉRGIO DANTAS DE OLIVEIRA JÚNIOR - INPA