Cellulosic biofuel represents a sustainable alternative to fossil fuels, yet high cellulase costs hinder its development. Thermostable cellulosomes, which function at elevated temperatures, increase reaction rates and reduce cooling costs by using cohesin-dockerin interactions to colocalize hyperthermostable cellulases. Due to the noncovalent nature of the cohesin-dockerin interaction, cellulosome stability has been limited to 75 °C. Our study leverages computational design and rapid screening to introduce two different intermolecular disulfide bridges between the same cohesin and dockerin, creating two disulfide cohesin-dockerin pairs. Both disulfide pairs withstood 100 °C and denaturing conditions. Furthermore, the two disulfide bridges retained their orthogonality, expanding the number of orthogonal cohesin-dockerin interactions. Finally, at the cellulase optimal temperature of 80 °C, disulfide assembly improved the activity of a bivalent cellulosome by 26% compared to that of its noncovalent counterpart. These disulfide cohesin-dockerin interactions can be used as building blocks to construct covalent protein complexes that can endure extreme temperatures.