Non-invasive online monitoring of polyol lipid production with Aureobasidium pullulans using fluorescence measurement

Abstract Polyol lipids (PLs) are biosurfactants produced by Aureobasidium pullulans , offering a promising, sustainable alternative to conventional surfactants from crude oil or palm oil. Online monitoring of product formation allows rapid process intensification. In this study, a new online monitoring method for PL formation is presented. Extracellular PL production was characterized in shake flasks using online monitoring of the respiratory activity. Three distinct phases of the process were identified: growth, PL production on glucose, and PL production on pullulan. With PL being fluorescent, an online fluorescence monitoring was developed. Therefore, 2D fluorescence spectra were recorded of PL solutions, revealing characteristic fluorescence. Based on these findings, specific wavelength combinations were evaluated for their online monitoring suitability during microtiter plate cultivations. Fluorescence measured at 540/580 nm (λ ex /λ em ) correlates well with the amount of PLs produced. Online fluorescence monitoring of PL-producing and non-producing strains revealed strong differences in fluorescence signals, validating the chosen wavelength combination. The here presented online product analytics minimizes analysis time, supports miniaturized and parallelized strain comparisons, and not at least may contribute to future process intensification.