Carica papaya by-products as new biocatalysts for the synthesis of oleic acid esters

摘要

Carica papaya lipase is a versatile biocatalyst that is employed for many biotechnological purposes. Its lipase activity was first observed to be tightly linked to the insoluble fraction of latex. Nevertheless, recent studies have shown that this activity is also present in the fruit peel and seeds, suggesting that the lipase activity occurs in other parts of the plant. In the present work, the hydrolytic activity on trioctanoin was determined in various plant by-products, including latex, leafs, petioles, meristems, fruits, and the stem. The most hydrolytic activity was found in the latex (11 U/mL), followed by the petioles (1.7 U/mL). The hydrolytic selectivity was determined using triacetin, tripropionin, tributyrin, and trioctanoin. The enzymes present in the latex showed a higher rate of hydrolysis of tributyrin, while those present in the petioles had a preference for tripropionin, possibly indicating the occurrence of at least two different triacylglycerol hydrolases. Five self-immobilized biocatalysts were obtained: lyophilized latex (LL), lyophilized petioles (LP), bagasse from petioles (BP), and, after a simple cold water washing treatment, treated lyophilized latex (TLL), and treated lyophilized petioles (TLP). This procedure yielded a 5- and 10-fold increase in the latex and petiole activity, respectively, on tributyrin. The selected biocatalysts, TLL and BP, were tested for the synthesis of oleic acid esters (OAE), reaching conversions over 80. Unexpectedly, only BP preferentially synthesized dodecyl oleate (DO) and showed the highest thermostability. Therefore, BP was further assayed for DO synthesis in a packed bed reactor (PBR), achieving 96 conversion over 40 h. This study shows the great potential of C. papaya by-products, particularly BP, as biocatalysts for the synthesis of OAE.