Effect of different gas environments on bench‐scale solid state fermentation of oat straw by white‐rot fungi

Abstract

Three white-rot fungi, Phanerochaete chrysosporium, Polyporus tulipiferae, and Polyporus sp. A336 were grown on 100-g amounts of chopped oat straw in gassed 4.5 L (diameter 16 cm, height 23 cm) solid-state reactors for two weeks. The different gas atmospheres were regulated by (1) air diffusion through foam plugs, (2) intermittent or continuous air flow, (3) intermittent oxygen, 50 or 100% continuous oxygen flow, and (4) continuous 10% carbon dioxide in oxygen flow. The fermented straw was analyzed for total weight loss, Klason lignin loss, and enzymatic (cellulase) hydrolysis. P. chrysosporium grown on straw in continuous oxygen at 35 degrees C caused a 41% weight loss and 33.5% hydrolysis was obtained when the pretreated straw was hydrolyzed with cellulase enzyme. P. tulipiferae caused a 27% weight loss and 34.3% cellulase hydrolysis in the straw at 30 degrees C. Polyporus sp. A336 selectively degraded lignin of the straw and under intermittent oxygen resulted in an 18% weight loss and 33.6% cellulase hydrolysis at 35 degrees C. When the straw was supplemented with 10% xylose (straw basis) and was continuously gassed with 50% oxygen, Polyporus sp. A336 produced a 14.5% weight loss and 38.7% cellulase hydrolysis. Oxygen and carbon dioxide exchange rates were measured for some of these bench-scale fermentations.

Effects of Oxygen and Carbon Dioxide Partial Pressures on Monascus Growth and Pigment Production in Solid‐State Fermentations

“…At constant carbon dioxide partial pressures of 0.02 atm, maximum pigment yields of red and yellow pigments were 1687.0 OD386 and 2426.9 OD495/g of IDS, respectively, at 0.50 atm of oxygen partial pressure. A similar effect was reported in fermentations by white-rot fungi of oat straw, where at least 0.50 atm of oxygen partial pressure might be needed for optimum lignin removal (Levonen-Munoz and Bone, 1985). Solid-state fermentations may have a heterogeneous gas environment, especially within a solid substrate particle.…”