“…Besides the optical spectroscopic techniques ultraviolet-visible (UV/Vis) and infrared (IR) spectroscopy, Raman spectroscopy coupled with chemometrics has found extensive applications in monitoring various processes for biopharmaceutical products, including raw material testing (Li et al, 2010), cell culture (Abu-Absi et al, 2011;Berry et al, 2015;Golabgir and Herwig, 2016), chromatography (Feidl et al, 2019;Rolinger et al, 2021;Wang et al, 2023), filtration (Rolinger et al, 2023), freezing (Roessl et al, 2014;Weber and Hubbuch, 2021), or formulation (Wei et al, 2022). For VLPs in particular, recent studies demonstrated the real-time monitoring of a baculovirus cultivation for the production of rabies VLPs (Guardalini et al, 2023a;b; as well as the cross-flow filtrationbased polishing operations such as dis-and reassembly of the HBcAg-VLPs (Rüdt et al, 2019;Hillebrandt et al, 2022). Despite the broad applicability of spectroscopic methods in biopharmaceutical processing, their application to precipitation processes is rather unexplored.…”