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A successful conversion of lignocellulosic biomass into biofuel could be achieved through an ionic liquids (ILs)-pretreatment and an enzyme saccharification. In this study, the fungal strains with high cellulase productions were isolated and identified as Penicillium janthinellum FHH1 and P. oxalicum FLY4. A high cellulase production was obtained at pH 4.0 and 30 °C for P. janthinellum FHH1 with corn stalk and beef extract for 9 days and for P. janthinellum FHH1 with corn stalk and peptone for 7 days. A pH range between 4.0 to 6.0 and a temperature range from 55 °C to 60 °C were applicable for cellulase with high activities during hydrolysis. A high NaCl-stability and a relatively high ILs-stability were found for cellulase obtained from P. oxalicum FLY4. High yields of reducing sugar were obtained by enzymatic hydrolysis of the original corn stalk and ILs-pretreated corn stalk. P. oxalicum FLY4 has a great potential for ILs-assisted fungi in the degradation of lignocellulosic biomass into value-added products.

Ionic liquids (ILs) are effective solvents for lignocellulose pretreatment. Enzymatic saccharification converts pretreated lignocelluloses into valuable products, and IL-tolerant cellulase improves the enzymatic efficiency and the reuse of ILs. In this study, a fungal strain with a relatively high cellulase production was isolated and identified as Aspergillus aculeatus G1-3. The high production of β-glucosidase (1.943 U per mL), CMCase (1.303 U per mL), and FPase (0.165 U per mL) was obtained using corn stover as the carbon source and peptone as the nitrogen source. The results were obtained at pH 8.0 and 30 °C with an inoculation size of 3% (volume per volume) for 7 days. A mutant strain Aspergillus aculeatus P6 with β-glucosidase (7.023 U per mL), CMCase (1.543 U per mL), and FPase (0.098 U per mL) was obtained by 60Co-γ irradiation. The cellulase activity was measured at pH 5.0 and 60 °C for enzymatic hydrolysis. The cellulase from mutant strains was stable in different concentrations of 1-ethyl-3-methylimidazolium acetate. Enzymatic saccharification of the original corn stover and ILs-pretreated corn stover was successfully performed with high sugar yields. The mutant strains of Aspergillus aculeatus have great potential for their further application in the conversion of lignocellulosic biomass into biofuels.

Phosphate-solubilizing microorganisms have been considered as a novel alternative approach to provide phosphate fertilizers that promote plant growth. In this study, three strains were isolated and identified as Penicillium oxalicum FJG21, Penicillium oxalicum FJQ5, and Bacillus subtilis BPM12, with a relatively high phosphate-solubilizing activity. Various phosphate sources were investigated, and Ca3(PO4)2 was identified as the effective phosphate source. Factors governing the phosphate-solubilizing activity of the strains included carbon and nitrogen sources, initial pH, and fermentation time. A high soluble phosphorus content was achieved with 529.0 μg·mL-1, 514.0 μg·mL-1, and 330.7 μg·mL-1 for Penicillium oxalicum FJG21, Penicillium oxalicum FJQ5, and Bacillus subtilis BPM12, respectively. An inverse correlation of the quantity of soluble phosphorus content and the pH value of the medium was observed. In addition, Bacillus subtilis BPM12 displayed a prominent capability of producing indole acetic acid. Penicillium oxalicum FJG21 and Penicillium oxalicum FJQ5 exhibited high cellulase activities. These phosphate-solubilizing microorganisms with good phosphate-solubilizing capability and growth-promoting ability are the promising strains for agricultural utilization.

There is increasing interest in the application of ionic liquids for the pretreatment and fractionation of lignocelluloses. In this study, a series of functional acidic ionic liquids (ILs) with various heterocyclic organic cations were synthesized. Corn stalks were successfully fractionated into lignin, hemicelluloses, and cellulose when ultrasonically pretreated with ILs at 70 °C for 3 h, and subsequently treated with alkaline extraction. High yields of IL-isolated lignin (18.3% to 19.6%) and (8.3% to 14.6%) were obtained using ILs in the absence and presence of water, respectively. The yield of cellulose ranged from 40.0 to 77.0% from IL treatments, whereas the yield of hemicelluloses ranged from 1.1% to 17.3%. Enzymatic hydrolysis of the isolated cellulose residual produced 89.2% to 94.9% reducing sugar with 77.8% to 86.1% glucose, which corresponded to 80.5% to 91.4% enzymatic conversion of cellulose. Syringol and vanillin were found as the main lignin degradation products.

Ionic liquid (IL)-assisted pretreatment is an important step in biochemical conversion of lignocellulosic biomass into biofuels. Design for low-cost ILs that efficiently work at a relatively low pretreatment temperature with a short processing time is of great interest. In this work, a functional acidic ionic liquid, 1-H-N-methyl-2-pyrrolidonium chloride ([Hnmp]Cl), was prepared by a simple synthetic procedure in a cost-effective manner and was then investigated for use in the pretreatment of lignocellulosic biomass. Factors including temperature, time, ratio of biomass to ionic liquid, and water content were studied to determine their impact on the pretreatment of lignocellulose; 91.39% of lignin content was recovered when the corn stalk was pretreated by pure [Hnmp]Cl at 100 °C for 45 min with a biomass loading of 5%. The highest glucose yield attained was 93.20% and the highest cellobiose yield was 18.76%, when the ratio of biomass to water was kept at 1:4. The pretreatment efficacy was dependent on the pretreatment temperature and processing time, which was more efficient for pure ionic liquid with respect to lignin recovery from lignocelluloses. However, more efficient enzymatic saccharification of cellulose-rich materials was achieved with aqueous ionic liquid.

Lignocellulosic biomass as a renewable and valuable resource has been a very active research area during recent years. Ionic liquids (ILs) are an attractive approach for the pretreatment of lignocelluloses. In this work, a series of pyrrolidinium-based ionic liquids were prepared simply and were investigated for the pretreatment of corn stalk at 90 °C for 30 min. The characteristics of regenerated lignin and cellulose-rich materials were determined by Fourier transform infrared spectroscopy (FTIR) analysis. Both ILs and ILs/H2O were studied. Notably, 10.17% lignin based on the original corn stalk was recovered with [Hmp]Cl-pretreatment; 21.34% and 15.83% reducing sugar based on the original corn stalk were observed during pretreatment with [Hmp]HSO4/H2O and [Hmp]Cl/H2O pretreatment, respectively; 80.54% of reducing sugar was obtained based on the cellulose-rich materials with [Hmp]Cl/H2O-pretreatment. Also, the glucose and cellobiose yields were 73.82% and 8.64%, respectively.