Immobilized enzyme holds considerable potential for industrial applications. In this study, a thermostable xylanase from Geobacillus thermodenitrificans X1 was subjected to carrier free immobilization to generate xylanase cross-linked enzyme aggregates (Xy-CLEAs). Xy-CLEAs were prepared by using overnight precooled (at - 20 degrees C) acetone as precipitant and glutaraldehyde (GA) as the cross-linker. A reaction time of 2 h, GA (0.01% v/v), protein concentration (1.67 mg/mL), 2 h precipitation time and protein to precipitant ratio of 1:10 were found to be the optimum conditions for Xy-CLEAs preparations. Morphological and structural characterization of CLEAs revealed their spherical shape with a diameter of 200-250 nm. In comparison to free xylanase, the immobilized xylanase had high relative activity at a diverse temperature and pH range. Thermostability and pH stability was also improved after immobilization of xylanase. CLEAs of xylanase proved to be commercially reliable as they retained 53.5% activity after being reused till six cycles and 86% activity after storage at 4 degrees C for 8 weeks.