In this study, pineapple cannery waste materials were used as substrate for the microbial production of vanillic acid and vanillin by Aspergillus niger I-1472 and Pycnoporus cinnabarinus MUCL 39533. Biotransformation of ferulic acid from pineapple waste by A. niger I-1472 to vanillic acid was optimized using Response Surface Methodology (RSM). A central composite rotatable design was used to allocate treatment combinations and factors tested for their influence on vanillic acid production were inoculum size, yeast extract concentration, diammonium tartrate concentration and initial medium pH. The amount of vanillic acid produced was used as the response for the fermentation study and was assumed to be under the influence of the four factors tested. The estimated conditions for optimal vanillic acid production were inoculum size, 3.08 ×105 CFU mL-1; yeast extract, 0.37 gL-1; diammonium tartrate, 3.88 gL-1 and initial pH, 4.3. Subsequent biotransformation of vanillic acid by P. cinnabarinus MUCL 39533 to vanillin was enhanced with the addition of resin. Under these optimal conditions, 141.00 mgL-1 of vanillin was produced from 5 g of pineapple cannery waste.
Protease is one of the most important industrial enzymes with a multitude of applications in both food and non-food sectors. Although most commercial proteases are microbial proteases, the potential of non-conventional protease sources, especially plants, should not be overlooked. In this study, horse mango (Mangifera foetida Lour) fruit, known to produce latex with a blistering effect upon contact with human skin, was chosen as a source of protease, and the effect of the extraction process on its protease activity evaluated. The crude enzyme was extracted from the kernels and extraction was optimized by a response surface methodology (RSM) using a central composite rotatable design (CCRD). The variables studied were pH (x(1)), CaCl(2) (x(2)), Triton X-100 (x(3)), and 1,4-dithryeitol (x(4)). The results obtained indicate that the quadratic model is significant for all the variables tested. Based on the RSM model generated, optimal extraction conditions were obtained at pH 6.0, 8.16 mM CaCl(2), 5.0% Triton X-100, and 10.0 mM DTT, and the estimated response was 95.5% (w/w). Verification test results showed that the difference between the calculated and the experimental protease activity value was only 2%. Based on the t-value, the effects of the variables arranged in ascending order of strength were CaCl(2) < pH < DTT < Triton X-100.
A rotatable central composite design (CCD) was used to study the effect of cryoprotectants (skim milk, sucrose and lactose) on the survival rate of a probiotic Lactobacillus strain, L. reuteri C10, for poultry, during freeze-drying and storage. Using response surface methodology, a quadratic polynomial equation was obtained for response value by multiple regression analyses: Y = 8.59546-0.01038 X(1)-0.09382 X(2)-0.07771 X(3)-0.054861 X(1)(2)-0.04603 X(3)(2)-0.10938 X(1)X(2). Based on the model predicted, sucrose exerted the strongest effect on the survival rate. At various combinations of cryoprotectants, the viability loss of the cells after freeze-drying was reduced from 1.65 log colony forming units (CFU)/mL to 0.26-0.66 log CFU/mL. The estimated optimum combination for enhancing the survival rate of L. reuteri C10 was 19.5% skim milk, 1% sucrose and 9% lactose. Verification experiments confirmed the validity of the predicted model. The storage life of freeze-dried L. reuteri C10 was markedly improved when cryoprotectants were used. At optimum combination of the cryoprotectants, the survival rates of freeze-dried L. reuteri C10 stored at 4°C and 30°C for 6 months were 96.4% and 73.8%, respectively. Total viability loss of cells which were not protected by cryoprotectants occurred after 12 and 8 weeks of storage at 4°C and 30°C, respectively.