Isolation and Immobilized Application of Limonin/Naringin-Degrading Bacteria for Microbial Debittering of Citrus Juice

This study aimed to screen limonin/naringin-degrading bacteria and assess their debittering potential by cell immobilization. Consequently, 50 bacterial strains with limonin-degrading ability were isolated and screened, among which BL-29 showed the highest limonin degradation rate (57.92%) and was identified as Citrobacter sp. with a naringin-degrading ability (39.17%) simultaneously. The limonin degradation rate reached 65.13% when the BL-29 inoculum volume was 4 mL (OD600 = 0.8), fermentation temperature was 42 °C, fermentation time was 30 h, initial pH was 3.0, and OP-10 concentration was 1% (v/v). Then, BL-29 was immobilized successfully using ZIF-8, sodium alginate (SA), and κ-carrageenan (κ-C), among which κ-C encapsulation was highly tolerant to pH and temperature variations. After being reused five times, its limonin-degrading activity (28.32%) was significantly higher than that of the control group. When applied to pomelo juice, the concentration of limonin and naringin decreased by 36.95% and 52.06%, respectively, demonstrating a great potential of debittering in citrus products.