Expression and Characterization of a Novel Mannanse From Achaetomium sp. Xz8 in Pichia pastoris Expression of a Xylanase Gene Originated from Rumen Anaerobic Fungi Neocallimastix frontalis in Pichia pastoris Expression of Chicken Neurexophilin 1 Gene in Pichia pastoris Effect of Co-expression of Vitreoscilla Hemoglobin on Expression of Β-mannanase in Pichia pastoris