Virus-like particles are very interesting tools for application in bionanotechnology, due to their monodisperse features and biocompatibility. In particular, the cowpea chlorotic mottle virus (CCMV) capsid has been studied extensively as it can be assembled and disassembled reversibly, facilitating cargo encapsulation. CCMV is, however, only stable at physiological conditions when its endogenous nucleic acid cargo is present. To gain more flexibility in the type of cargo encapsulated and to broaden the window of operation, it is interesting to improve the stability of the empty virus-like particles. Here, a method is described to utilize the CCMV capsid at close to physiological conditions as a stable, enzyme filled nanoreactor. As a proof-of-principle, the encapsulation of T4 lysozyme (T4L) was chosen; this enzyme is a promising antibiotic, but its clinical application is hampered by, for example, its cationic character. It was shown that four T4L molecules can successfully be encapsulated inside CCMV capsids, while remaining catalytically active, which could thus improve the enzyme's application potential.