A tubular bioreactor containing fluidized biocatalyst(s), which has a structure of a tubular circuit in a closed loop, comprising porous tubular membrane module(s) (1) constituting at least a portion of the tubular circuit, through which membrane product(s) may pass or permeate;
    a tubular hollowed member coaxial about and spaced from the said membrane module, which tubular part has an outlet(s) (5) for discharging the product(s) from the tubular circuit structure;
    an inlet (4) for feeding substrate(s), which inlet may be mounted on the wall of the below mentioned connecting tubing(s);
    a means for circulating the said mixture flow containing a substrate(s), the biocatalyst(s), and the product(s), in the said tubular circuit structure; and
    tubing(s) connecting the said membrane module and the said circulating means.