I would recommend silica beads (0.1 mm, lysing matrix B) in combination with a benchtop homogenizer (e.g. FastPrep, Ribolyser, PreCellys). 3 times for 30 seconds at 6,000 rpm and, in between, storage of samples on ice for 30 seconds. The enzyme activity is maintained and the beads even disrupt bacilli spores.
We have had good success when using a M-110Y microfluidizer. Maybe you might need to treat the cells before hand with enzymes to disrupt the cell wall i.e. lysozyme. Also you can look at modifying the buffer you are disrupting you sample in? For example, a 50 mM Tris 50 mM EDTA (TE) buffer (pH 8) with lysozyme. However this is all dependent on what you are disrupting your cells for i.e. isolation of inclusions, isolation of membrane etc.