Optimization of limonin invertase production by scaling up aspergillus tabingensis UA13 fermentation to a 5-liter scale.

Abstract

The enzymatic approach is a highly effective and the major scientific method to eliminating bitter components in citrus-derived products nowadays. Microbial production of limonin invertase stands out due to its pivotal role in the removal of the bitter substance, limonin. The optimization of fermentation parameters and the study of scale-up fermentation are imperative for product commercialization. In this study, we focused on optimizing stirring speed, fermentation temperature, and initial pH to enhance the growth and limonin invertase production by the Aspergillus tabin (A. tabin) strain UA13 in a 5-liter stirred-tank bioreactor. Our results revealed the following optimal parameters are: a stirring speed of 300rpm, a fermentation temperature of 35 °C and a pH 5.0. Under these optimized conditions, the limonin invertase activity reached its peak at 63.38U mL-1, representing a 1.67-fold increase compared to the unoptimized conditions (38.10U mL-1), while also reducing the fermentation duration by 12 hours. Furthermore, our research demonstrated that limonin invertase effectively hydrolyze limonin in grapefruit juice, reducing its content from 13.28μg mL-1 to 2.14μg mL-1, as determined by HPLC, resulting in a 6.21-fold reduction of the bitter substance.