too little if any selective pressure which infers that its evolutionary potential is likely untapped the present disclosure provides the solution to the two major barriers preventing commercialization of photosynthetic hydrogen production to date 1 the hydrogenase enzyme that produces the molecular hydrogen is sensitive to oxygen and 2 the amount of hydrogen production needs to be increased since the c reinhardtii hydrogenase genes have been cloned mutation of the original parental genes is disclosed herein as well as a method to search among a library of such mutants and select a mutant algal hydrogenase with an improved phenotype with respect to hydrogen production rate after the mutant genes are created this disclosure further describes insertion and expression of the mutants in c reinhardtii a novel method of selecting or screening the mutants for enhanced traits in algae is also disclosed the present disclosure further provides for a chimeric hydrogenase with a mutation s that decreases the diameter of the proton channels described above thereby restricting the larger oxygen molecules by size exclusion while still allowing for passage of the smaller bio hydrogen molecules as will be further apparent from the examples provided herein below the present disclosure encompasses methods for mutating bacterial hydrogenases to produce increased amounts of hydrogen after just one round of a combinatorial shuffle additionally exogenous dna of hydrogenases can be successfully re introduced into the genome of c reinhardtii.