BACKGROUND:　Monascus　fermentation　byproduct　(MFB)　is　a　biowaste　generated　after　food　colorants　are　extracted.　Using　MFB　to　produce　probiotics　(Bacillus　subtilis)　is　a　sustainable　way　for　the　entire　production　to　be　used　as　food　or　animal　feed　additives.　However,　due　to　the　rigidity　of　the　Monascus　mycelium　cell　wall,　B.　subtilis　cannot　sufficiently　utilize　the　nutrients　in　MFB,　leading　to　low　biomass　production　efficiency.　We　studied　the　effects　of　ultrasonic　treatment,　papain,　beta-glucanase,　and　chitosanase,　and　their　combinations　on　improving　the　levels　of　soluble　components　from　MFB.　The　effects　of　these　treatments　on　mycelium　cell　walls　were　visualized　using　scanning　electron　microscopy,　and　their　influence　on　B.　subtilis　production　was　analyzed.　RESULTS:　Ultrasonic　treatment　increased　the　soluble　components　by　210　g　kg(-1),　including　50　g　kg(-1)　protein　and　120　g　kg(-1)　carbohydrates.　An　enzyme　mixture　increased　the　soluble　components　by　160　g　kg(-1),　including　30　g　kg(-1)　protein　and　90　g　kg(-1)　carbohydrates.　The　combination　of　the　two　methods　achieved　the　highest　increase　of　soluble　components　(up　to　400　g　kg(-1))　leading　to　a　maximum　B.　subtilis　production　of　1　x　10(11)　colony-forming　unit　mL(-1).　This　yield　was　about　20　times　greater　than　that　using　untreated　MFB　and　about　eight　times　greater　than　treatments　using　only　ultrasonic　or　enzymatic　methods.　CONCLUSION:　The　productivity　of　B.　subtilis　production　using　MFB　as　the　sole　medium　can　be　greatly　improved　by　ultrasound　or　enzymes,　which　cause　the　release　of　intercellular　components　or　cell　wall　components.　(c)　2020　Society　of　Chemical　Industry