A novel microbial approach for the valorisation of lupanine containing wastewater emitted from the lupin beans processing industry

Abstract

Lupin bean processing industries commonly use the debittering process for eliminating the antinutritional and alkaloid content of lupin beans, ensuring a safe product for human consumption. Various debittering processes have been developed for the removal of toxic and bitter alkaloids from lupin beans. However, these methods require the use of large amounts of water, which is eventually disposed as wastewater rich in alkaloids. Lupanine constitutes the major quinolizidine alkaloid present in the specific type of wastewater, which is contained in the effluent as an enantiomeric mixture of D-(+)-lupanine and L-(–)-lupanine. Lupanine is considered a useful molecule exhibiting several applications in pharmaceutical/medical agricultural and chemical industries. Therefore, microbial valorisation of lupanine constitutes a promising approach for the management of wastewater generated from the lupin bean snack industry. Microorganisms capable of metabolizing racemic lupanine were isolated from different environmental sources, which were identified based on phylogenetic and physiological characteristics. Rhodococcus rhodochrous LPK211, Rhodococcus ruber LPK111, Rhodococcus sp. LPK311 and Pseudomonas putida LPK411 were capable of biodegrading racemic lupanine as a single carbon source while generating known and novel lupanine-based alkaloid structures as end products from racemic lupanine bioconversion. Moreover, all strains achieved enantioselective resolutions of lupanine racemate, producing L-(–)-lupanine in high enantiomeric excess. Based on preliminary findings, the most effective isolated strain (P. putida LPK411) was further subjected to an extensive study. The aforementioned strain could perform enantioselective resolution of lupanine enantiomeric mixtures existing in both unrefined and pretreated industrial wastewater employing a lab-scale bioreactor while assessing the capacity of LPK411 to perform racemic resolution of lupanine in a repeated fed-batch process exhibited that the microorganism could repetitively perform stable enantioselective resolution. Furthermore, the transcriptional kinetics of key genes for the degradation of lupanine by LPK411 was investigated revealing the transcriptional patterns of the metabolic pathway employed for lupanine metabolism, while an environmental toxicological assessment was performed to evaluate the impact of lupanine and other natural compounds on the ecosystems.