Optimization of xylanase production by filamentous fungi in solid state fermentation and scale-up to horizontal tube bioreactor

Five microorganisms, namely Aspergillus niger CECT 2700, A. niger CECT 2915, A. niger CECT 2088, Aspergillus terreus CECT 2808, and Rhizopus stolonifer CECT 2344, were grown on corncob to produce cell wall polysaccharide-degrading enzymes, mainly xylanases, by solid-state fermentation (SSF). A. niger CECT 2700 produced the highest amount of xylanases of 504±7 U/g dry corncob (dcc) after 3 days of fermentation. The optimization of the culture broth (5.0 g/L NaNO3, 1.3 g/L (NH4)2SO4, 4.5 g/L KH2PO4, and 3 g/L yeast extract) and operational conditions (5 g of bed loading, using an initial substrate to moistening medium of 1:3.6 (w/v)) allowed increasing the predicted maximal xylanase activity up to 2,452.7 U/g dcc. However, different pretreatments of materials, including destarching, autoclaving, microwave, and alkaline treatments, were detrimental. Finally, the process was successfully established in a laboratory-scale horizontal tube biore- actor, achieving the highest xylanase activity (2,926 U/g dcc) at a flow rate of 0.2 L/min. The result showed an overall 5.8-fold increase in xylanase activity after optimization of culture media, operational conditions, and scale-up.We are grateful to the Spanish Ministry of Science and Innovation for the financial support of this work (project CTQ2011-28967), which has partial financial support from the FEDER funds of the European Union; to the Leonardo da Vinci Programme for founding the stay of Felisbela Oliveira in Vigo University; to MAEC-AECID (Spanish Government) for the financial support for Perez-Bibbins, B. and to Spanish Ministry of Education, Culture and Sports for Perez-Rodriguez's FPU; and to Solla E. and Mendez J. (CACTI-University of Vigo) for their excellent technical assistance in microscopy

Direct use of spent mushroom substrate from Pleurotus pulmonarius as a readily delignified feedstock for cellulase production

The feasibility of spent mushroom substrate (SMS) as an alternative fermentation feedstock for cellulase production has been demonstrated in this work. Utilization of SMS as a substrate has been attempted widely due to its high cellulose content and readily available in smaller particle size. On top of that, the availability of delignified SMS by the action of Pleurotus pulmonarius during mushroom cultivation offers another benefit to its use whereby no chemical pretreatment would be required prior to fermentation. The recovery of crude laccase and manganese peroxidase from delignified SMS were found to be 3 and 1.4 U/g, respectively. Further to this, the cellulase production from SMS by Trichoderma asperellum UPM 1 under solid state fermentation was optimized by applying central composite design, resulted in increment of 1.4-fold in CMCase (171.21 U/g) and 1.5-fold in β-glucosidase (6.83 U/g), with the optimum temperature of 27.5 °C, initial moisture content 81% and initial pH of fermentation 4.5. Therefore, this study showed that the direct utilization of SMS is feasible for promising cellulase production by T. asperellum UPM 1

Use of elephant grass (Pennisetum purpureum) as substrate for cellulase and xylanase production in solid-state cultivation by Penicillium echinulatum

<div><p>Abstract The high cost of the enzymes used for the hydrolysis of lignocellulosic biomass is one of the bottlenecks in the production of second-generation ethanol and the use of local biomass, such elephant grass, can help to reduce this cost. In this investigation elephant grass biomass was evaluated as a carbon and inducer source of production of cellulases and xylanases by the fungus Penicillium echinulatum strain 9A02S1 in solid-state cultivation. The highest filter paper activity (13.26 U.g-1 dry matter) and β-glucosidase activity (138.34 U.g-1 dry matter) were obtained on the fifth day of cultivation, in medium containing biomass pre-treated with sulfuric acid and untreated, respectively. The highest endoglucanase activity was 158.44 U.g-1 dry matter in the presence of elephant grass pre-treated with sulfuric acid. The xylanase activity was highest with medium that was formulated with 75% untreated elephant grass and 25% wheat bran (372.62 U.g-1 dry matter). In conclusion, the results showed that it is possible to obtain large amounts of cellulases and xylanases using a cosmopolitan and very low cost substrate such as elephant grass.</p></div