The last technology we will look at is biological pretreatment. Lignin is removed from lignocellulosic biomass through lignin-degrading microorganisms. Key parameters are temperature, cultivation time, nutrient addition, and selectivity on lignin. Some of the lignin-degrading enzymes include lignin peroxidase, manganese peroxidase, laccase, and xylanase. Advantages to using a system such as this include: no chemicals, mild conditions (ambient temperature and pressure), low energy and low capital outlay, and less enzyme use later on. However, pretreatments take days to weeks, loss of cellulose and hemicellulose, contaminants, and additional pretreatment for higher sugar yield.