Deproteinization of natural rubber by the coupling action of protease and microwave energy

Abstract

Protein allergens in NRL and NRP may cause life threatening (latex allergy) Type I in hypersensitive users. Thus, the purpose of this research is to develop a new grade of natural rubber with low protein allergen by using protease and microwave energy. The criterion of deproteinization is determined by monitoring from reduction of per cent nitrogen content from initial % nitrogen content in fresh latex. Based on hypothesis that microwave energy IS a high frequency electromagnetic field (2450 MHz) that induces the polar molecules in latex to rotate due to alternate change of electromagnetic field resulting rapid and homogenous heating. The rubber particles and proteins associated with rubber particle were deformed and loosen. Addition of protease thereafter should lead to more rapid enzyme activity and higher efficiency. It is expected that deproteinization of latex will be accomplished in shorter time. The results show that use of microwave energy and papain can reduce 80% protein in latex within 10 minutes as measured by total nitrogen content compared with the initial nitrogen content Scaling up of the reaction volume to 5 liter of latex, using the same process. DPNR obtained showed 0.18 g% of the nitrogen content or 60% nitrogen reduction from the initial value, and the volatile matters were reduced equally to 0.18%. The other non-rubber components namely ash (0.31%). dirt (0.03%) and color index (3.6) were slightly higher than control (CDPNR). The results show that protein and lipid in DPNR were significantly decreased. The processibility properties such as initial plasticity (Po=27), plasticity retention index (PRI=63%) were lower than standard specifications of STR5L (Po=35, PRI=65), but the Mooney viscosity (58) does not change. The results show that in the compounding of DPNR to make rubber products, more antioxidant should be added to increase the shelf life. The water extractable protein (WEP=143 µg/g) is significantly lower than control deproteimzed natural rubber (CDPNR-413 µg/g) and STR5L (640 µg/g). The WEP from DPNR is significantly lower than concentrated latex 60% and some glove samples. Analysis of molecular size of WEP from DPNR by SDS-PAGE showed no protein band in the range of 14-30 kD. Results from Enzyme allergosorbent test (EAST) indicated that there was no protein antigen in DPNR that reacted with latex specific-lgE in 41 serum samples previously checked with in the concentrated latex 60%. Using skin prick test (SPT) to compare the wheal size in one latex sensitive person confirmed that no wheal was obseived with WEP from DPNR. while positive wheals were observed with protein allergen from CDPNR and gloves. EAST was used to study the prevalence of rubber allergic hypersensitivity in the 3-group of human serum samples (100 persons/group): Group 1. genera! healthy persons: Group 2. the general atopic patients: and Group 3, the healthcare workers. Positive EAST to WEP from concentrated latex 60% used as standard protein allergen, was 13.7% (41/300 samples) which is divided to 3%of Group 1 (3/100 samples). 8% of Group 2 (8/100 samples) and 30% of Group 3 (3000 samples). The result is similar to the reports in other countries for general healthy person but higher than other reports in the healthcare workers (Group 3). In conclusion, microwave energy improves the efficiency of papain in removing protein from natural rubber, by decreasing the WEP. in the molecular weight range of 14-30 kD which are protein allergen, yielding DPNR which is safe for high-risk allergic people and healthcare workers who are involved with NRP.