Prospecting of soybean hulls as an inducer carbon source for the cellulase production

The combination of continuous-pulse feeding hydrolysates with soybean hulls induction during fed-batch fermentation of Trichoderma reesei b5 significantly elevated the cellulase production and its degradation ability on lignocellulosic biomass

To date, the high cost of cellulase is still a major factor limiting industrial production of lignocellulose bioconversion. This study developed a novel strategy combining continuous-pulse feeding glucose with soybean hulls (SBH) induction to efficiently elevate cellulase production by Trichoderma reesei b5 and enhance hydrolysis performance of cellulase on lignocellulose. In this strategy, the sugar concentration in the fermentation system was strictly controlled to meet the sugar requirements of strain for enzyme production without inhibition. Using SBH instead of microcrystalline cellulose effectively enhanced cellulase secretion as well as improved the enzyme system compositions, causing the improvement of hydrolysis performance. Using this strategy, filter-paperase (FPase) activity in the fermentation broth was more than ten-folds higher than that in batch fermentation (6.0 U/mL vs. 75.9 U/mL), and achieved the highest β-glucosidase activity reported in the literature to date (905 U/mL). This study also confirmed the feasibility of using on-site produced enzymatic hydrolysates instead of glucose as feeding medium. It provides a feasible process for large-scale production of low-cost and efficient cellulase, which is of great significance for the construction of "sugar platforms" based on lignocellulose and industrialization of lignocellulosic bioconversion.

Production of cellulase by Novosphingobium sp. Cm1 and its potential application in lignocellulosic waste hydrolysis

Management of lignocellulosic wastes in and around the municipality area requires special consideration. Continuous deposition of these wastes to the nearby areas led to gradual deterioration of the environment. The objective of this study was to produce cellulase from the bacteria isolated from the unexplored rainforest of NE-India for lignocellulosic waste hydrolysis. Based on carboxymethyl cellulose utilization and the congo red test, Novosphingobium sp. Cm1 was found to be the most promising strain out of 114 bacterial isolates and the strain was selected for further study. The optimization of the fermentative conditions for maximum enzyme activity was carried out using one factor-at-a-time strategy and the optimum pH, temperature and incubation time was recorded as pH 5, 37 °C and 96 h respectively. The maximum β-1,4-endoglucanase activity was observed with 1.5% CMC (5.1 ± 0.05 U/mL) and 0.25% yeast extract (7.6 ± 0.72 U/mL). The bacterial waste hydrolysis ability was investigated using three wastes where vegetable waste showed maximum activity of 3.4 ± 0.48 U/mL. Bacterial interaction and waste utilization were verified using Scanning Electron Microscope and Fourier-Transform infrared spectroscopy analysis. The present study confirmed the promising ability of Novosphingobium sp. to waste hydrolysis. Further investigations may lead to new possibilities for low-cost enzyme production that will help to meet the rising cellulase demand.

Soybean hulls as carbohydrate feedstock for medium to high-value biomolecule production in biorefineries: A review

Soybean is one of the major world crops, with an annual production of 359 million tons. Each ton of processed soybean generates 50-80 kg of soybean hulls (SHs), representing 5-8% of the whole seed. Due to environmental concerns and great economic potential, the search of SHs re-use solutions are deeply discussed. The lignocellulosic composition of SHs has attracted the attention of the scientific and productive sector. Recently, some studies have reported the use of SHs in the production of medium to high value-added molecules, with potential applications in food and feed, agriculture, bioenergy, and other segments. This review presents biotechnological approaches and processes for the management and exploitation of SHs, including pre-treatment methods and fermentation techniques, for the production of different biomolecules. Great potentialities and innovations were found concerning SH exploration and valorisation of the soybean chain under a biorefinery and circular bioeconomy optic.

Assessment and evaluation of cellulase production using ragi (Eleusine coracana) husk as a substrate from thermo-acidophilic Aspergillus fumigatus JCM 10253

The cellulase production by filamentous fungi Aspergillus fumigatus JCM 10253 was carried out using agro-industrial waste ragi husk as a substrate in the microbial fermentation. The effect of the process parameters such as temperature, substrate concentration, pH, and incubation process time and their interdependence was studied using response surface methodology. The optimum cellulase activities were obtained at 50 °C under the conditions with 1-2% of substrate concentration at pH 2-4 for the incubation period of 7-8 days. The maximum carboxymethyl cellulase (CMCase) and β-glucosidase activities with optimized process variables were 95.2 IU/mL and 0.174 IU/mL, respectively. The morphological characterization of fungus by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) revealed the presence of secondary protein structures. Furthermore, this study demonstrated that the application of ragi husk could be a promising feedstock for value-added industrial products. The thermo-acidophilic nature of isolated strain Aspergillus fumigatus JCM 10253 possessed a significant potential for higher titer of cellulase production that could be further employed for lignocellulosic bioethanol production.