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Fiber Expansion (fiber + expansion)
Kinds of Fiber Expansion Selected AbstractsAlkali-based AFEX pretreatment for the conversion of sugarcane bagasse and cane leaf residues to ethanolBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Chandraraj Krishnan Abstract Sugarcane is one of the major agricultural crops cultivated in tropical climate regions of the world. Each tonne of raw cane production is associated with the generation of 130,kg dry weight of bagasse after juice extraction and 250,kg dry weight of cane leaf residue postharvest. The annual world production of sugarcane is ,1.6 billion tones, generating 279 MMT tones of biomass residues (bagasse and cane leaf matter) that would be available for cellulosic ethanol production. Here, we investigated the production of cellulosic ethanol from sugar cane bagasse and sugar cane leaf residue using an alkaline pretreatment: ammonia fiber expansion (AFEX). The AFEX pretreatment improved the accessibility of cellulose and hemicelluloses to enzymes during hydrolysis by breaking down the ester linkages and other lignin carbohydrate complex (LCC) bonds and the sugar produced by this process is found to be highly fermentable. The maximum glucan conversion of AFEX pretreated bagasse and cane leaf residue by cellulases was ,85%. Supplementation with hemicellulases during enzymatic hydrolysis improved the xylan conversion up to 95,98%. Xylanase supplementation also contributed to a marginal improvement in the glucan conversion. AFEX-treated cane leaf residue was found to have a greater enzymatic digestibility compared to AFEX-treated bagasse. Co-fermentation of glucose and xylose, produced from high solid loading (6% glucan) hydrolysis of AFEX-treated bagasse and cane leaf residue, using the recombinant Saccharomyces cerevisiae (424A LNH-ST) produced 34,36,g/L of ethanol with 92% theoretical yield. These results demonstrate that AFEX pretreatment is a viable process for conversion of bagasse and cane leaf residue into cellulosic ethanol. Biotechnol. Bioeng. 2010;107: 441,450. © 2010 Wiley Periodicals, Inc. [source] Effect of enzyme supplementation at moderate cellulase loadings on initial glucose and xylose release from corn stover solids pretreated by leading technologiesBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Rajeev Kumar Abstract Moderate loadings of cellulase enzyme supplemented with ,-glucosidase were applied to solids produced by ammonia fiber expansion (AFEX), ammonia recycle (ARP), controlled pH, dilute sulfuric acid, lime, and sulfur dioxide pretreatments to better understand factors that control glucose and xylose release following 24, 48, and 72 h of hydrolysis and define promising routes to reducing enzyme demands. Glucose removal was higher from all pretreatments than from Avicel cellulose at lower enzyme loadings, but sugar release was a bit lower for solids prepared by dilute sulfuric acid in the Sunds system and by controlled pH pretreatment than from Avicel at higher protein loadings. Inhibition by cellobiose was observed to depend on the type of substrate and pretreatment and hydrolysis times, with a corresponding impact of ,-glucosidase supplementation. Furthermore, for the first time, xylobiose and higher xylooligomers were shown to inhibit enzymatic hydrolysis of pure glucan, pure xylan, and pretreated corn stover, and xylose, xylobiose, and xylotriose were shown to have progressively greater effects on hydrolysis rates. Consistent with this, addition of xylanase and ,-xylosidase improved performance significantly. For a combined mass loading of cellulase and ,-glucosidase of 16.1 mg/g original glucan (about 7.5 FPU/g), glucose release from pretreated solids ranged from 50% to75% of the theoretical maximum and was greater for all pretreatments at all protein loadings compared to pure Avicel cellulose except for solids from controlled pH pretreatment and from dilute acid pretreatment by the Sunds pilot unit. The fraction of xylose released from pretreated solids was always less than for glucose, with the upper limit being about 60% of the maximum for ARP and the Sunds dilute acid pretreatments at a very high protein mass loading of 116 mg/g glucan (about 60 FPU). Biotechnol. Bioeng. 2009;102: 457,467. © 2008 Wiley Periodicals, Inc. [source] Access of cellulase to cellulose and lignin for poplar solids produced by leading pretreatment technologiesBIOTECHNOLOGY PROGRESS, Issue 3 2009Rajeev Kumar Abstract Adsorption of cellulase on solids resulting from pretreatment of poplar wood by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), controlled pH, dilute acid (DA), flowthrough (FT), lime, and sulfur dioxide (SO2) and pure Avicel glucan was measured at 4°C, as were adsorption and desorption of cellulase and adsorption of ,-glucosidase for lignin left after enzymatic digestion of the solids from these pretreatments. From this, Langmuir adsorption parameters, cellulose accessibility to cellulase, and the effectiveness of cellulase adsorbed on poplar solids were estimated, and the effect of delignification on cellulase effectiveness was determined. Furthermore, Avicel hydrolysis inhibition by enzymatic and acid lignin of poplar solids was studied. Flowthrough pretreated solids showed the highest maximum cellulase adsorption capacity (,solids = 195 mg/g solid) followed by dilute acid (,solids = 170.0 mg/g solid) and lime pretreated solids (,solids = 150.8 mg/g solid), whereas controlled pH pretreated solids had the lowest (,solids = 56 mg/g solid). Lime pretreated solids also had the highest cellulose accessibility (,cellulose = 241 mg/g cellulose) followed by FT and DA. AFEX lignin had the lowest cellulase adsorption capacity (,lignin = 57 mg/g lignin) followed by dilute acid lignin (,lignin = 74 mg/g lignin). AFEX lignin also had the lowest ,-glucosidase capacity (,lignin = 66.6 mg/g lignin), while lignin from SO2 (,lignin = 320 mg/g lignin) followed by dilute acid had the highest (301 mg/g lignin). Furthermore, SO2 followed by dilute acid pretreated solids gave the highest cellulase effectiveness, but delignification enhanced cellulase effectiveness more for high pH than low pH pretreatments, suggesting that lignin impedes access of enzymes to xylan more than to glucan, which in turn affects glucan accessibility. In addition, lignin from enzymatic digestion of AFEX and dilute acid pretreated solids inhibited Avicel hydrolysis less than ARP and flowthrough lignin, whereas acid lignin from unpretreated poplar inhibited enzymes the most. Irreversible binding of cellulase to lignin varied with pretreatment type and desorption method. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Effects of cellulase and xylanase enzymes on the deconstruction of solids from pretreatment of poplar by leading technologiesBIOTECHNOLOGY PROGRESS, Issue 2 2009Rajeev Kumar Abstract Comparative data is presented on glucose and xylose release for enzymatic hydrolysis of solids produced by pretreatment of poplar wood by ammonia fiber expansion (AFEX), ammonia recycled percolation (ARP), controlled pH, dilute acid, flowthrough (FT), lime, and sulfur dioxide (SO2) technologies. Sugar solubilization was measured for times of up to 72 h using cellulase supplemented with ,-glucosidase at an activity ratio of 1:2, respectively, at combined protein mass loadings of 5.8,116 mg/g of glucan in poplar wood prior to pretreatment. In addition, the enzyme cocktail was augmented with up to 11.0 g of xylanase protein per gram of cellulase protein at combined cellulase and ,-glucosidase mass loadings of 14.5 and 29.0 mg protein (about 7.5 and 15 FPU, respectively)/g of original potential glucose to evaluate cellulase,xylanase interactions. All pretreated poplar solids required high protein loadings to realize good sugar yields via enzymatic hydrolysis, and performance tended to be better for low pH pretreatments by dilute sulfuric acid and sulfur dioxide, possibly due to higher xylose removal. Glucose release increased nearly linearly with residual xylose removal by enzymes for all pretreatments, xylanase leverage on glucan removal decreased at high cellulase loadings. Washing the solids improved digestion for all pretreatments and was particularly beneficial for controlled pH pretreatment. Furthermore, incubation of pretreated solids with BSA, Tween 20, or PEG6000 prior to adding enzymes enhanced yields, but the effectiveness of these additives varied with the type of pretreatment. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Comparative sugar recovery and fermentation data following pretreatment of poplar wood by leading technologiesBIOTECHNOLOGY PROGRESS, Issue 2 2009Charles E. Wyman Abstract Through a Biomass Refining Consortium for Applied Fundamentals and Innovation among Auburn University, Dartmouth College, Michigan State University, the National Renewable Energy Laboratory, Purdue University, Texas A&M University, the University of British Columbia, and the University of California at Riverside, leading pretreatment technologies based on ammonia fiber expansion, aqueous ammonia recycle, dilute sulfuric acid, lime, neutral pH, and sulfur dioxide were applied to a single source of poplar wood, and the remaining solids from each technology were hydrolyzed to sugars using the same enzymes. Identical analytical methods and a consistent material balance methodology were employed to develop comparative performance data for each combination of pretreatment and enzymes. Overall, compared to data with corn stover employed previously, the results showed that poplar was more recalcitrant to conversion to sugars and that sugar yields from the combined operations of pretreatment and enzymatic hydrolysis varied more among pretreatments. However, application of more severe pretreatment conditions gave good yields from sulfur dioxide and lime, and a recombinant yeast strain fermented the mixed stream of glucose and xylose sugars released by enzymatic hydrolysis of water washed solids from all pretreatments to ethanol with similarly high yields. An Agricultural and Industrial Advisory Board followed progress and helped steer the research to meet scientific and commercial needs. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] | ||||||||||