What does photosynthetic biomass mean

Photosynthetic creates biomass that can be converted to renewable bioenergy. Residues from plants and animals and microbial biomass can be converted by microorganisms to useful energy outputs, including methane, hydrogen or electricity. 

The answer to this will be from your lab notes/procedure. it would be best to ask another student who participated in the lab as we do not know what was done, what enzyme or if the temperature is celsius or fahrenheit. if i were to guess though i'd say the rate stopped due to enzyme denturing at high temperature