Production of cellulolytic enzymes from fungi and use in the saccharification of palm cake and palm fibre

Aspergillus niger ATCC 6275 possesses the highest carboxymethyl-cellulase, xylanase and -glucosidase activities under liquid and solid cultivations compared withMyceliophthora thermophila IFO 31843 and an isolate, F11. Palm cake proved to be a better substrate for enzyme production and saccharification than palm fibre. Saccharification of these two substrates, using crude enzyme solutions from three fungi and commercial enzymes, was investigated.     

Xylanase production in solid-state fermentation: a study of its properties

Summary Xylanase production by Aspergillus niger van Tieghem was studied in solid-state cultivation. The screening of substrates was carried out in column incubators aerated with humidified air at 30°C. Results of physiological studies showed that the best yield of xylanase was 2500 U/g dry matter on a mixture of straw+bran 1:1 at 70% of moisture content.In order to compare some properties of the xylanase produced in both liquid and solid cultures, A. niger was also grown on xylan in submerged cultures. The enzymes produced in solid and liquid cultures have an optimum pH of about 3.8 and 4.5, respectively. Xylanase synthetized in solid fermentation is a little more thermostable than that from liquid culture and is maximally active at 50° C, compared to 45° C for enzyme from liquid culture.     

Simultaneous production and induction of cellulolytic and xylanolytic enzymes in aStreptomyces sp.

Extracellular cellulolytic and xylanolytic enzymes ofStreptomyces sp. EC22 were produced during submerged fermentation. The cell-free culture supernatant of the streptomycete grown on microcrystalline cellulose contained enzymes able to depolymerize both crystalline and soluble celluloses and xylans. Higher cellulase and xylanase activities were found in the cell-free culture supernatant of the strain when grown on microcrystalline cellulose than when grown on xylan. Total cellulase and endoglucanase [carboxymethyl-cellulase (CMCase)] activities reached maxima after 72 h and xylanase activity was maximal after 60h. Temperature and pH optima were 55°C and 5.0 for CMCase activity and 60°C and 5.5 for total crystalline cellulase and xylanase activities. At 80°C, approximate half-lives of the enzymes were 37, 81 and 51 min for CMCase, crystalline cellulose depolymerization and xylanase, respectively.     

Comprehensive studies on optimization of cellulase and xylanase production by a local indigenous fungus strain via solid state fermentation using oil palm frond as substrate

The high cost of cellulases remains the most significant barrier to the economical production of bio-ethanol from lignocellulosic biomass. The goal of this study was to optimize cellulases and xylanase production by a local indigenous fungus strain (Aspergillus niger DWA8) using agricultural waste (oil palm frond [OPF]) as substrate. The enzyme production profile before optimization indicated that the highest carboxymethyl cellulose (CMCase), filter paper (FPase), and xylanase activities of 1.06 U/g, 2.55 U/g, and 2.93 U/g were obtained on day 5, day 4, and day 5 of fermentation, respectively. Response surface methodology was used to study the effects of several key process parameters in order to optimize cellulase production. Of the five physical and two chemical factors tested, only moisture content of 75% (w/w) and substrate amount of 2.5 g had statistically significant effect on enzymes production. Under optimized conditions of 2.5 g of substrate, 75% (w/w) moisture content, initial medium of pH 4.5, 1 × 10⁶ spores/mL of inoculum, and incubation at ambient temperature (±30°C) without additional carbon and nitrogen, the highest CMCase, FPase, and xylanase activities obtained were 2.38 U/g, 2.47 U/g, and 5.23 U/g, respectively. Thus, the optimization process increased CMCase and xylanase production by 124.5 and 78.5%, respectively. Moreover, A. niger DWA8 produced reasonably good cellulase and xylanase titers using OPF as the substrate when compared with previous researcher finding. The enzymes produced by this process could be further use to hydrolyze biomass to generate reducing sugars, which are the feedstock for bioethanol production.     

Production and potential applications of a xylanase from a new strain of Streptomyces cuspidosporus

Enzyme production by a new mesophilic Streptomyces isolate was investigated which grew optimally on 1% (w/v) xylan and 10% (w/v) wheat bran at pH 7 and 37 °C. Xylan induced only CMCase (0.29 U/ml) besides xylanase (22–35 U/ml, 40–49 U/mg protein). Wheat bran induced xylanase (105 U/ml, 17.5 U/mg protein), CMCase (0.74 U/ml), -xylosidase (0.009 U/ml), -glucosidase (0.026 U/ml), -L-arabinofuranosidase (0.049 U/ml), amylase (1.6 U/ml) and phytase (0.432 U/ml). The isolate was amenable to solid state cultivation and produced increased levels of xylanase (146 U/ml, 28 U/mg protein). The pH and temperature optima of the crude xylanase activity were 5.5 and 65 °C respectively. The pI was 6.0 as determined by PEG precipitation. The crude enzyme was applied in treatment of paper pulp and predigestion of poultry feed and was found to be effective in releasing sugars from both and soluble phosphorus from the latter.     

Production of Cellulase-Free Xylanase from Bacillus megaterium by Solid State Fermentation for Biobleaching of Pulp

Xylanase production from B. megaterium was enhanced using solid state fermentation with respect to the use of solid substrate, moistening solution, moisture content, inoculum, sugars, soyabean meal, amino acids, and extraction with surfactant. An increase of ≈423-fold in xylanase production and complete suppression of CMCase production was achieved over submerged liquid fermentation. Biobleaching using this cellulase-free xylanase, 8 U/g of oven dried pulp of 10% consistency, showed 8.12% and 1.16% increase in brightness and viscosity, 13.67% decrease in kappa number, and 31% decrease in chlorine consumption at the CD stage.     

Xylanase production under solid-state fermentation and its characterization by an isolated strain of <Emphasis Type="Italic">Aspergillus foetidus</Emphasis> in India

Summary A locally isolated strain of Aspergillus foetidus MTCC 4898 was studied for xylanase (EC 3.2.1.8) production using lignocellulosic substrates under solid state fermentation. Corncobs were found as the best substrates for high yield of xylanases with poor cellulase production. The influence of various parameters such as temperature, pH, moistening agents, moisture level, nitrogen sources and pretreatment of substrates were evaluated with respect to xylanase yield, specific activity and cellulase production. Influence of nitrogen sources on protease secretion was also examined. Maximum xylanase production (3065 U/g) was obtained on untreated corncobs moistened with modified Mandels and Strenberg medium, pH 5.0 at 1 5 moisture levels at 30 °C in 4 days of cultivation. Submerged fermentation under the same conditions gave higher yield (3300 U/g) in 5 days of cultivation, but productivity was less. Ammonium sulphate fractionation yielded 3.56-fold purified xylanase with 76% recovery. Optimum pH and temperature for xylanase activity were found to be 5.3 and 50 °C respectively. Kinetic parameters like K_m and V_max were found to be 3.58 mg/ml and 570 μmol/mg/min. Activity of the enzyme was found to be enhanced by cystiene hydrochloride, CoCl₂, xylose and Tween 80, while significantly inhibited by Hg⁺⁺, Cu⁺⁺ and glucose. The enzyme was found to be stable at 40 °C. The half life at 50 °C was 57.53 min. However thermostability was enhanced by glycerol, trehalose and Ca⁺⁺. The crude enzyme was stable during lyophilization and could be stored at less than 0 °C.     

Production of cellulases and hemicellulases by Aspergillus niger KK2 from lignocellulosic biomass

To investigate the production of cellulases and hemicellulases from Aspergillus niger KK2, solid state fermentation (SSF) was performed by using different ratios of rice straw and wheat bran. When A. niger KK2 was grown on rice straw alone as a solid support in SSF, the maximum FPase activity was 19.5 IU g(-1) in 4 days. Also, CMCase (129 IU g(-1)), beta-glucosidase (100 IU g(-1)), xylanase (5070 IU g(-1)) and beta-xylosidase (193 IU g(-1)) activities were concurrently obtained after 5-6 days of fermentation. The higher enzyme activities produced by A. niger KK2 is a significant advantage from the viewpoint of practical saccharification reaction. Cellulases and hemicellulases produced by A. niger KK2 might be applied to pulp and paper industry, feed industry and chemical industry.     

Tamarind seed powder and palm kernel cake: two novel agro residues for the production of tannase under solid state fermentation by Aspergillus niger ATCC 16620

Palm kernel cake (PKC), the residue obtained after extraction of palm oil from oil palm seeds and tamarind seed powder (TSP) obtained after removing the fruit pulp from tamarind fruit pod were tested for the production of tannase under solid-state fermentation (SSF) using Aspergillus niger ATCC 16620. The fungal strain was grown on the substrates without any pretreatment. In PKC medium, a maximum enzyme yield of 13.03 IU/g dry substrate (gds) was obtained when SSF was carried out at 30 degrees C, 53.5% initial substrate moisture, 33 x 10(9) spores/5 g substrate inoculum size and 5% tannic acid as additional carbon source after 96 h of fermentation. In TSP medium, maximum tannase yield of 6.44 IU/gds was obtained at 30 degrees C, 65.75% initial substrate moisture, 11 x 10(9) spores/5 g substrate inoculum, 1% glycerol as additional carbon source and 1% potassium nitrate as additional nitrogen source after 120 h of fermentation. Results from the study are promising for the economic utilization and value addition of these important agro residues, which are abundantly available in many tropical and subtropical countries.     

Saccharification of Kans grass using enzyme mixture from Trichoderma reesei for bioethanol production

Bioethanol is one of the alternatives of the conventional fossil fuel. In present study, effect of different carbon sources on the production of cellulolytic enzyme (CMCase) from Trichoderma reesei at different temperatures, duration and pH were investigated and conditions were optimized. Acid treated Kans grass (Saccharum sponteneum) was subjected to enzymatic hydrolysis to produce fermentable sugars which was then fermented to bioethanol using Saccharomyces cerevisiae. The maximum CMCase production was found to be 1.46 U mL⁻¹ at optimum condition (28 °C, pH 5 and cellulose as carbon source). The cellulases and xylanase activity were found to be 1.12 FPU g⁻¹ and 6.63 U mL⁻¹, respectively. Maximum total sugar was found to be 69.08 mg/g dry biomass with 20 FPU g⁻¹ dry biomass of enzyme dosage under optimum condition. Similar results were obtained when it was treated with pure enzyme. Upon fermentation of enzymatic hydrolysate, the yield of ethanol was calculated to be 0.46 g g⁻¹.     

Production of multi-fiber modifying enzyme from Mamillisphaeria sp. for refining of recycled paper pulp

Enzymatic modification of pulp is receiving increasing interest for energy reduction at the refining step of the paper-making process. In this study, the production of a multi-fiber modifying enzyme from Mamillisphaeria sp. BCC8893 was optimized in submerged fermentation using a response-surface methodology. Maximal production was obtained in a complex medium comprising wheat bran, soybean, and rice bran supplemented with yeast extract at pH 6.0 and a harvest time of 7 d, resulting in 9.2 IU/mL of carboxymethyl cellulase (CMCase), 14.9 IU/mL of filter paper activity (FPase), and 242.7 IU/mL of xylanase. Treatment of old corrugated container pulp at 0.2-0.3 IU of CMCase/g of pulp led to reductions in refining energy of 8.5-14.8%. The major physical properties were retained, including tensile and compression strength. Proteomic analysis showed that the enzyme was a complex composite of endo-glucanases, cellobiohydrolases, beta-1,4-xylanases, and beta-glucanases belonging to various glycosyl hydrolase families, suggestive of cooperative enzyme action in fiber modification, providing the basis for refining efficiency.     

Alkaline-active xylanase produced by an alkaliphilicBacillus sp isolated from kraft pulp

ABacillus sp (V1-4) was isolated from hardwood kraft pulp. It was capable of growing in diluted kraft black liquor at pH 11.5 and produced 49 IU (mol xylose min^–1 ml^–1) of xylanase when cultivated in alkaline medium at pH 9. Maximal enzyme activity was obtained by cultivation in a defined alkaline medium with 2% birchwood xylan and 1% corn steep liquor at pH 9, but high enzyme production was also obtained on wheat bran. The apparent pH optimum of the enzyme varied with the pH used for cultivation and the buffer system employed for enzyme assay. With cultivation at pH 10 and assays performed in glycine buffer, maximal activity was observed at pH 8.5; with phosphate buffer, maximal activity was between pH 6 and 7. The xylanase temperature optimum (at pH 7.0) was 55°C. In the absence of substrate, at pH 9.0, the enzyme was stable at 50°C for at least 30 min. Elecrophoretic analysis of the crude preparation showed one predominant xylanase with an alkaline pl. Biobleaching studies showed that the enzyme would brighten both hardwood and softwood kraft pulp and release chromophores at pH 7 and 9. Because kraft pulps are alkaline, this enzyme could be used for prebleaching with minimal pH adjustment.     

Production of cellulases and xylanase by Aspergillus fumigatus SK1 using untreated oil palm trunk through solid state fermentation

Direct utilization of untreated oil palm trunk (OPT) for cellulases and xylanase production by Aspergillus fumigatus SK1 was conducted under solid-state fermentation (SSF). The highest activities of extracellular cellulases and xylanases were produced at 80% moisture level, initial pH 5.0, 1 × 10⁸ spore/g (inoculum) with 125 μm of OPT as sole carbon source. The cellulases and xylanase activities obtained were 54.27, 3.36, 4.54 and 418.70 U/g substrates for endoglucanase (CMCase), exoglucanase (FPase), β-glucosidase and xylanase respectively. The crude cellulases and xylanase required acidic condition to retain their optimum activities (pH 4.0). Crude cellulases and xylanase were more stable at 40 °C compared to their optimum activities conditions (60 °C for FPase and 70 °C for CMCase, β-glucosidase and xylanase). SDS-PAGE and zymogram analysis showed that Aspergillus fumigatus SK1 could secrete cellulases (endoglucanase, exoglucanase and β-glucosidase), xylanase and protease. Enzymatic degradation of alkaline treated OPT with concentrated crude cellulases and xylanases resulted in producing polyoses.     

Studies on cellulase production by a Bacillus subtilis

Bacillus subtilis AU-1 was found to produce carboxymethylcellulase (CMCase) and Avicelase activities in the culture supernatant when grown on a variety of carbohydrates as major carbon source. Maximum CMCase production was obtained in a liquid medium containing 0.2% D (+) raffinose as inducer, 0.5% each of yeast extract, casamino acids and proteose peptone at 50 °C and at an initial pH of 6.0. CMCase activity was detected at early log phase of growth, and reached the maximum level at early stationary phase of growth which occurred at the 10th hour of cultivation. The optimal temperature for CMCase activity was 65 °C, and the enzyme was highly stable up to 60 °C. CMCase synthesis was subjected to catabolite repression by glucose and cellobiose.     

Enzymatic saccharification of sugar cane bagasse by continuous xylanase and cellulase production from cellulomonas flavigena PR‐22

Cellulase (CMCase) and xylanase enzyme production and saccharification of sugar cane bagasse were coupled into two stages and named enzyme production and sugar cane bagasse saccharification. The performance of Cellulomonas flavigena (Cf) PR‐22 cultured in a bubble column reactor (BCR) was compared to that in a stirred tank reactor (STR). Cells cultured in the BCR presented higher yields and productivity of both CMCase and xylanase activities than those grown in the STR configuration. A continuous culture with Cf PR‐22 was run in the BCR using 1% alkali‐pretreated sugar cane bagasse and mineral media, at dilution rates ranging from 0.04 to 0.22 1/h. The highest enzymatic productivity values were found at 0.08 1/h with 1846.4 ± 126.4 and 101.6 ± 5.6 U/L·h for xylanase and CMCase, respectively. Effluent from the BCR in steady state was transferred to an enzymatic reactor operated in fed‐batch mode with an initial load of 75 g of pretreated sugar cane bagasse; saccharification was then performed in an STR at 55°C and 300 rpm for 90 h. The constant addition of fresh enzyme as well as the increase in time of contact with the substrate increased the total soluble sugar concentration 83% compared to the value obtained in a batch enzymatic reactor. This advantageous strategy may be used for industrial enzyme pretreatment and saccharification of lignocellulosic wastes to be used in bioethanol and chemicals production from lignocellulose. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:321–326, 2016     

Optimization of cellulase production in batch fermentation byTrichoderma reesei

Maximum cellulase production was sought by comparing the activities of the cellulases produced by differentTrichoderma reesei strains andAspergillus niger. Trichoderma reesei Rut-C30 showed higher cellulase activity than otherTrichoderma reesei strains andAspergillus niger that was isolated from soil. By optimizing the cultivation condition during shake flask culture, higher cellulase production could be achieved. The FP (filter paper) activity of 3.7 U/ml and CMCase (Carboxymethylcellulase) activity of 60 U/ml were obtained from shake flask culture. When it was grown in 2.5L fermentor, where pH and DO levels are controlled, the Enzyme activities were 133.35 U/ml (CMCase) and 11.67 U./ml (FP), respectively. Ammonium sulfate precipitation method was used to recover enzymes from fermentation broth. The dried cellulase powder showed 3074.9 U/g of CMCase activity and 166.7 U/g of FP activity with 83.5% CMCase recovery.     

Studies on xylanase fromBasidiomycetes

Formation of extracellular xylanase was studied in 10 strains of wood-destroying fungi belonging to Basidiomycetes during their submerged cultivation with willow sawdust. The highest enzyme activity was found in the fungus Trametes hirsuta (Wulf.) Pilát. The effect of sources of carbon and nitrogen, cultivation time and initial pH of the cultivation solution on the formation of xylanase by the fungus Trametes hirsuta was investigated. The highest production of the enzyme was reached during cultivation in the presence of willow sawdust, asparagine and at the initial pH of 5.0. The presence of xylanase, cellulase, mannanase and amylase as well as of beta-xylosidase, beta-glucosidase, beta-mannosidase and beta-galactosidase was demonstrated in the enzyme preparation obtained after a 10-day submerged cultivation of Trametes hirsuta under optimal conditions.     

Selection of a strain of Aspergillus for the production of citric acid from pineapple waste in solid-state fermentation

Aspergillus foetidus ACM 3996 (=FRR 3558) and three strains of Aspergillus niger ACM 4992 (=ATCC 9142), ACM 4993 (=ATCC 10577), ACM 4994 (=ATCC 12846) were compared for the production of citric acid from pineapple peel in solid-state fermentation. A. niger ACM 4992 produced the highest amount of citric acid, with a yield of 19.4g of citric acid per 100g of dry fermented pineapple waste under optimum conditions, representing a yield of 0.74g citric acid/g sugar consumed. Optimal conditions were 65% (w/w) initial moisture content, 3% (v/w) methanol, 30°C, an unadjusted initial pH of 3.4, a particle size of 2mm and 5ppm Fe²⁺. Citric acid production was best in flasks, with lower yields being obtained in tray and rotating drum bioreactors.     

Production and activities of chitinases and hydrophobins from Lecanicillium lecanii

The production of chitinases and hydrophobins from Lecanicillium lecanii was influenced by the cultivation method and type of carbon source. Crude enzyme obtained from solid-substrate culture presented activities of exochitinases (32 and 51 kDa), endochitinases (26 kDa), β-N-acetylhexosaminidases (61, 80, 96 and 111 kDa). Additionally, submerged cultures produced exochitinases (32 and 45 kDa), endochitinases (10 and 26 kDa) and β-N-acetylhexosaminidases (61, 96 and 111 kDa). β-N-acetylhexosaminidases activity determined in solid-substrate culture with added chitin was ca. threefold (7.58 ± 0.57 U mg⁻¹) higher than submerged culture (2.73 + 0.57 U mg⁻¹). Similarly, hydrophobins displayed higher activities in solid-substrate culture (627.3 ± 2 μg protein mL⁻¹) than the submerged one (57.4 ± 4.7 μg protein mL⁻¹). Molecular weight of hydrophobins produced in solid-substrate culture was 7.6 kDa and they displayed surface activity on Teflon.     

Lentinus edodes and Pleurotus species lignocellulolytic enzymes activity in submerged and solid-state fermentation of lignocellulosic wastes of different composition

Lentinus edodes and Pleurotus species from various origins were compared for the first time for their ability to produce lignocellulolytic enzyme in solid-state (SSF) and submerged (SF) fermentation of various plant raw material. Fungi cultivation in identical culture conditions revealed wide differences among both species and strains of the same species. The yields of CMCase (62.3Uml(-1)), xylanase (84.1 U ml(-1)), FPA (5.9 U ml(-1)), and laccase (4103 Ul(-1)) are the best so far obtained with the strains of oyster mushrooms. The study pointed out that the nature of lignocellulosic material and the method of fungi cultivation are factors determining the expression of lignocellulolytic potential of fungi as well as the ratio of individual enzymes in enzyme complex. SSF of tree leaves is favorable for laccase and MnP secretion by the majority L. edodes and Pleurotus strains, whereas SF provides better production of hydrolytic enzymes.