The researchers tested the effect of adding extra xylanase (hemicellulase) to the process of turning corn stover and rice straw into ethanol. They used a method called LMAA to treat the plant materials before testing. When they added more xylanase to the mix, they saw that the breakdown of the plant fibers into sugars improved significantly. But interestingly, higher amounts of xylanase led to a decrease in ethanol production. They also found that using a lower amount of starter culture resulted in higher ethanol production. So, while adding extra xylanase helps break down the plant material better, it might not always lead to more ethanol being produced.