The present invention comprises an in vitro enzymatic process that effectively converts renewable polysaccharides into high yields of hydrogen at mild conditions, using only enzymes and water. The process comprises a number of enzymes: (1) phosphorylases, (2) phosphoglucomutases, (3) hydrogenases, and (4) enzymes involved in the pentose-phosphate pathway. Preferred embodiments of the process produce only hydrogen and carbon dioxide as net products, translating into an inexpensive method of generating hydrogen in very large quantities from low-cost feedstocks.