Corncob Residue Research Articles

Valorisation of corncob residues to functionalised porous carbonaceous materials for the simultaneous esterification/transesterification of waste oils

Functionalised porous carbonaceous materials prepared from the controlled pyrolysis of corncobs were found to provide excellent activities in the simultaneous esterification/transesterification of highly acidic waste oils to biodiesel-like mixtures. Materials carbonised at 600 °C (mostly microporous) containing –SO3H groups (ca. 1 wt% S, 0.16 mmol g−1 –SO3H) exhibited the optimum yields (>95%) to fatty acid methyl esters after 6 h of reaction.

Biorefinery for bioethanol, lactic acid, xylitol and astaxanthin production from corn cobs

A biorefinery is an integrated process for biomass conversion to produce multiple products including fuels and chemicals. For successful developmentofbiorefinery, it is important toachieve the rational design of the total biorefinery system for high profitability with low environmental impact. In this view, we experimentally examined the feasibility of biorefinery for producing multiple products including bioethanol, xylitol, lactic acid and astaxanthin from corn cobs as a feed stock. The corn cobs were first hydrolysed by the dilute acid to obtain to xylose and its residues were then enzymatically hydrolyzed to glucose. By this treatment, hydrolysates containing approximately 27 g-xylose/l and 26 g-glucose/l were selectively obtained from 100 g-corn cobs/l. Using the hydrolysate containing xylose, approximately 18g/l xylitol was successfully produced by Candida magnolia. Thehydrolysate containingglucosewaseasilyutilized for bioethanol production by Saccharomyces cerevisiae. Simultaneous enzymatic saccharification and fermentation (SFF) was also effective to produce bioethanol and lactic acid from corn cob residues treated by dilute sulphuric acid, which mainly contain cellulose. It was also found that the hydrolysates containing xylose and glucose could be used as a favourable source for astaxanthin production using Xanthophyllomyces dentrohous. By incorporating the high value product such as astaxanthin into the biorefinery system, the economic feasibility of the biorefinery was greatly improved. Finally total process evaluation will be presented from the view points of profitability, energy consumption and environmental impact.

Statistical optimization of sulfite pretreatment of corncob residues for high concentration ethanol production

In this study, a central composite design of response surface method was used to optimize sulfite pretreatment of corncob residues, in respect to sulfite charge (5-10%), treatment time (1-2h), liquid/solid (l/s) ratio (6:1-10:1) and temperature (150-180°C) for maximizing glucose production in enzymatic hydrolysis process. The relative optimum condition was obtained as follows: sulfite charge 7.1%, l/s ratio 7.6:1, temperature 156°C for 1.4h, corresponding to 79.3% total glucan converted to glucose+cellobiose. In the subsequent simultaneous saccharification and fermentation (SSF) experiments using 15% glucan substrates pretreated under this kind of conditions, 60.8 g ethanol l(-1) with 72.2% theoretical yield was obtained.

Development of the cellulolytic fungus Trichoderma reesei strain with enhanced β-glucosidase and filter paper activity using strong artifical cellobiohydrolase 1 promoter

To improve the beta-glucosidase yield and total cellulase activity of Trichoderma reesei, extracellular beta-glucosidase (BGLI) was overexpressed under the control of the modified four-copy cbh1 promoter. Three transformants B2, B12 and B15 with successful integration of the bgl1 gene expression cassette were obtained, which exhibited 3.7-, 2.0- and 1.8-fold increase in beta-glucosidase activity than the parental strain RUT C30, respectively. The filter paper activities of the productive transformants B12 and B15 were improved by up to 130% and 55%, respectively. Saccharification of corncob residue with the crude enzyme dosages showed that the reducing sugar yields of B12 (5.59 mg/ml) and B15 (4.80 mg/ml) were 29% and 11% higher than that of RUT C30 (4.34 mg/ml), respectively. The present results proved that the modified four-copy cbh1 promoter was a useful tool for improving the cellulase activity of T. reesei, and the engineering strains developed in this study could be potentially used as promising cell factories for beta-glucosidase or cellulase production.

Development of succinic acid production from corncob hydrolysate by Actinobacillus succinogenes

Succinic acid is one of the most important platform chemicals since it has great potential in industrial applications. In this study, corncob hydrolysate was used for succinic acid production. After diluted acid treatment, xylose was released from hemicellulose as the predominant monosaccharide in the hydrolysate, whereas glucose was released very little and most was retained as cellulose in the raw material. Without any detoxification, corncob hydrolysate was used directly as the carbon source in the fermentation. Actinobacillus succinogenes could utilize the sugars in the hydrolysate to produce succinic acid efficiently. Through medium optimization, yeast extract was selected as the nitrogen source and MgCO3 was used to control pH. A total of 23.64 g/l of succinic acid was produced with a yield of 0.58 g/g based on consumed sugar, indicating that the waste corncob residue can be used to produce value-added chemicals practically.

Isolation and characterization of a β-glucosidase from Penicillium decumbens and improving hydrolysis of corncob residue by using it as cellulase supplementation

A β-glucosidase from Penicillium decumbens was purified and characterized. The enzyme presented as a single band of 120kDa on SDS-PAGE, showed optimal temperature of 65–70°C and optimal pH of 4.5–5.0. The β-glucosidase showed relatively higher affinity to pNPG and the highest affinity to salicin with the Km value as 0.0064 and 0.0188mM, respectively. The gene coding for it was obtained with an ORF of 2586bp coding for 861 amino acids belonging to glycoside hydrolases family 3. The purified enzyme could improve the saccharifying ability of cellulose when it was added to the cellulase systems of Trichoderma reesei QM 9414. The several properties of it, including its pH and temperature optima, the high affinity to substrates and high specific activity, make it has great potential to be utilized as supplementation in conversion of corncob residue and other lignocellulosic biomass into simple sugars.

High concentration ethanol production from corncob residues by fed-batch strategy

Ethanol production from corncob residues (CCR) pretreated by different methods was studied. The structure features of these CCR were analyzed by Fourier transform-infrared spectrum (FT-IR), X-ray diffraction (XRD), and field emission scanning electron microscope (SEM). Simultaneous saccharification and fermentation (SSF) was performed by adding crude cellulase preparations from Penicillium decumbens JUA10-1 at 30°C. The results suggested that different pretreatments resulted in different composition and structure of residues; these changes had a significant influence on ethanol productivity and concentration. The fed-batch method was combined with SSF to enhance ethanol concentration further and reduce enzyme dosage. Moreover, the absorption and desorption phenomena of cellobiohydrolase I (CBH I) (70kDa) were observed to be related to lignin contents in residues. These results demonstrated that despite the application of low enzyme dosage, high concentration ethanol could be produced from pretreated corncobs by combining fed-batch method with SSF.

Enhanced enzymatic conversion and glucose production via two-step enzymatic hydrolysis of corncob residue from xylo-oligosaccharides producer's waste

A study was conducted to investigate the hydrolysis of cellulose-enriched corncob residue, a cellulosic waste from the xylo-oligosaccharides industry, by two processes. The corncob residue was hydrolyzed by cellulases via direct hydrolysis and two-step hydrolysis. Cellulases were produced by Trichoderma reesei RutC-30 with kraft pulp as the substrate. When the cellulase dosage was above 8 FPU•g-1 of corncob residue and the corncob residue concentration was 3%, over 90% hydrolysis yield and 49.99% glucose yield were obtained at 48 h. To enhance the hydrolysis yield of corncob residue, a new process coupling enzymatic hydrolysis, separation, and acid treatment was investigated. The corncob residue was first hydrolyzed using cellulase for 24 h. Then the remaining solids of corncob residue was separated from the liquid containing soluble oligosaccharides, and allowed to subsequently hydrolyze, using the adsorbed enzyme for 24 h. Using this method, the total hydrolysis yield was up to 97.60%, which represents an increase by 7.5% in comparison to the direct 48 h enzymatic hydrolysis. When the hydrolysates of the two-step enzymatic process were subjected to the concentrated acid hydrolysis at 110 ºC for 2 h, the glucose yield could be increased from 43% to 90%.

Genome shuffling improves production of cellulase byPenicillium decumbensJU-A10

Improvement of cellulase production of Penicillium decumbens by genome shuffling of an industrial catabolite-repression-resistant strain JU-A10 with its mutants. After two rounds of genome shuffling, three fusants, GS2-15, GS2-21 and GS2-22, were obtained, showing 100%, 109% and 94% increase in FPase activity than JU-A10 respectively. The cellulase production of the fusants on various substrates, such as corn stover, wheat straw, bagasse and the corncob residue, was studied. The maximum productivities of GS2-15, GS2-21 and GS2-22 were 92.15, 102.63 and 92.35 FPU l(-1) h(-1) on the corncob residue at 44 h respectively, which were 117%, 142% and 118% higher than that of JU-A10 (42.44 FPU l(-1) h(-1), at 90 h). The improvements of the fusants were possibly because of their enhanced growth rates, earlier cellulase synthesis and higher secretion of extracellular proteins. The fusants obtained after genome shuffling could produce abundant cellulase much earlier, and they could be potential candidates for bioconversion process. This is the first report on the improvement of cellulase production in fungi by genome shuffling, and this is a good technique to improve other important phenotypes in fungi.

Lactic acid production from cellulosic waste by immobilized cells of Lactobacillus delbrueckii

Industrial waste corn cob residue (from xylose manufacturing) without pretreatment was hydrolyzed by cellulase and cellobiase. The cellulosic hydrolysate contained 52.4 g l−1 of glucose and was used as carbon source for lactic acid fermentation by cells of Lactobacillus delbrueckii ZU-S2 immobilized in calcium alginate gel beads. The final concentration of lactic acid and the yield of lactic acid from glucose were 48.7 g l−1 and 95.2%, respectively, which were comparative to the results of pure glucose fermentation. The immobilized cells were quite stable and reusable, and the average yield of lactic acid from glucose in the hydrolysate was 95.0% in 12 repeated batches of fermentation. The suitable dilution rate of continuous fermentation process was 0.13 h−1, and the yield of lactic acid from glucose and the productivity were 92.4% and 5.746 g l−1 h−1, respectively. The production of lactic acid by simultaneous saccharification and fermentation (SSF) process was carried out in a coupling bioreactor, the final concentration of lactic acid was 55.6 g l−1, the conversion efficiency of lactic acid from cellulose was 91.3% and the productivity was 0.927 g l−1 h−1. By using fed-batch technique in the SSF process, the final concentration of lactic acid and the productivity increased to 107.6 g l−1 and 1.345 g l−1 h−1, respectively, while the dosage of cellulase per gram substrate decreased greatly. This research work should advance the bioconversion of renewable cellulosic resources and reduce environmental pollution.

Lactic Acid Production From Cellulosic Material by Synergetic Hydrolysis and Fermentation

The hydrolysis process on corncob residue was catalyzed synergetically by the cellulase from Trichoderma reesei and the immobilized cellobiase. The feedback inhibition to cellulase reaction caused by the accumulation of cellobiose was eliminated efficiently. The hydrolysis yield of corncob residue was 82.5%, and the percentage of glucose in the reducing sugar reached 88.2%. The glucose in the cellulosic hydrolysate could be converted into lactic acid effectively by the immobilized cells of Lactobacillus delbrueckii. When the enzymatic hydrolysis of cellulose and the fermentation of lactic acid were coupled together, no glucose was accumulated in the reaction system, and the feedback inhibition caused by glucose was also eliminated. Under the batch process of synergetic hydrolysis and lactic acid fermentation with 100 g/L of cellulosic substrate, the conversion efficiency of lactic acid from cellulose and the productivity of lactic acid reached 92.4% and 0.938 g/ (L.h), respectively. By using a fed-batch technique, the total concentration of cellulosic substrate and lactic acid in the synergetic process increased to 200 and 107.5 g/L, respectively, whereas the dosage of cellulase reduced from 20 to 15 IU/g of substrate in the batch process. The results of the bioconversion of renewable cellulosic resources were significant.

High-yield cellulase production by Trichoderma reesei ZU-02 on corn cob residue

Cellulase production using corn cob residue from xylose manufacture as substrate was carried out by Trichoderma reesei ZU-02. It was found that on the same cellulose basis, the cellulase activity and yield produced on corn cob residue were comparable with that on purified cellulose. Under batch process, the optimum concentration of substrate was 40 g/l and the optimum C/N ratio was 8.0. In 500 ml flasks, cellulase activity reached 5.25 IU/ml (213.4 IU/g cellulose) after seven days’ cultivation. In a 30 m 3 stirred fermenter for large scale production, cellulase and cellobiase activity were 5.48 IU/ml (222.8 IU/g cellulase) and 0.25 IU/ml (10.2 IU/g cellulose), respectively, after four days’ submerged fermentation. The produced cellulase could effectively hydrolyze the corn cob residue, and the yield of enzymatic hydrolysis reached 90.4% on 10% corn cob residue (w/v) when the cellulase dosage was 20 IU/g substrate.

Remediation of Ammonium-Contaminated Abandoned Animal Waste Lagoon Soil: Physical Properties and Growth of Barley

Remediation of the soil beneath closed animal waste lagoons is an important issue, particularly for lagoons in environmentally sensitive regions. Few studies address the possibility of using plants to remediate these soils. The objectives of this research were to determine whether barley (Hor-deum vulgare L.), a salt-tolerant crop, would grow in lagoon soil and to determine the effect of plant residue amendments on barley growth and soil physical properties. The lagoon soil was collected from a closed swine lagoon. Oat-straw and corn-cob residues were added at rates of 0 (control), 15, 30, 45, 60, and 75 g/kg lagoon soil. Barley grew in all soils, including the soil with no residues. Average grain yield of plants in pots with oat straw was more than twice that of plants in pots with corn cobs (10.7 g/pot and 4.5 g/pot, respectively). Bulk density and oxygen diffusion rate decreased with increasing amounts of residue in the soil. Infiltration was lower in pots with oat straw than in pots with corn cobs. Irrigation water moved rapidly through macropores visible in the soil with corn cobs. The soil amended with corn cobs retained less water, causing poor growth of the barley. The results showed that corn-cob residue created preferential flow paths in the lagoon soil.

Cellulase production by solid state fermentation on lignocellulosic waste from the xylose industry

Cellulase production was carried out by solid state fermentation using corncob residue, a lignocellulosic waste from the xylose industry, as the substrate of Trichoderma reesei ZU-02. The effects of water content, dosage of wheat bran and initial pH value in solid substrate on cellulase synthesis were studied in shallow tray fermentors. The solid substrate could be reused in at least three batches and the highest cellulase activity (158 IFPU/g koji) was obtained in the second fermentation batch. To produce cellulase on a larger scale, a deep trough fermentor with forced aeration was used and 128 IFPU/g koji (∼305 IFPU/g cellulose) was reached after 5 days solid state fermentation. The enzyme koji produced in the present process can be used directly to hydrolyze corncob residue effectively, when the cellulase dosage was above 20 IFPU/g substrate, the saccharification yield could be over 84%.

Humic fertilizers by oxidative ammoniation of hydrolyzed corncob residues

Hydrolyzed corncob residues were oxiammoniated to obtain humic fertilizers. Samples were oxidized with nitric acid at the optimum conditions: T=353 K, nitric acid concentration=15 wt%, and reaction time=30 min. The oxidized product was further ammoniated in liquid phase for a range of operating variables. The final product is a water-soluble fraction that contains most of the nitrogen (10-14 wt%) while the solid fraction has a very low nitrogen content (<2 wt%)