Among different pectinases, pectin lyase seems to be the only pectic enzyme capable of breaking down pectin with a high degree of esterification. Trichoderma harziamun is excellent pectinases producer, therefore different isolates were screened by quantitative and qualitative methods. Screening results showed that two isolates showed maximum pectin lyase. Different fermentation conditions like fermentation rate, inoculum size, concentration of peptone, concentration of yeast extract, pH and tween -80 were optimized by different experiments for production of pectin lyase by T. harzianum...