Influences of Media Compositions on Characteristics of Isolated Bacteria Exhibiting Lignocellulolytic Activities from Various Environmental Sites

Efficient isolation of lignocellulolytic bacteria is essential for the utilization of lignocellulosic biomass. In this study, bacteria with cellulolytic, xylanolytic, and lignolytic activities were isolated from environmental sites such as mountain, wetland, and mudflat using isolation media containing the combination of lignocellulose components (cellulose, xylan, and lignin). Eighty-nine isolates from the isolation media were characterized by analyzing taxonomic ranks and cellulolytic, xylanolytic, and lignolytic activities. Most of the cellulolytic bacteria showed multienzymatic activities including xylanolytic activity. The isolation media without lignin were efficient in isolating bacteria exhibiting multienzymatic activities even including lignolytic activity, whereas a lignin-containing medium was effective to isolate bacteria exhibiting lignolytic activity only. Multienzymatic activities were mainly observed in Bacillus and Streptomyces, while Burkholderia was the most abundant genus with lignolytic activity only. This study provides insight into isolation medium for efficient isolation of lignocellulose-degrading microorganisms.     

Enzymatic degradation of Lignin-Carbohydrate complex (part I)

Initial steps in an early metabolic pathway of biodegradation of lignin by white-rot fungus are very important for application of biotechnology to the utilization of biomass; for example, enzymatic pretreatment for ethanol production from plant resources and biological pulping. Lignins in woody plants exist as giant high molecular weight compounds bounded with carbohydrates, mainly hemicelluloses at middle lamella and in secondary cell wall, and show resistance against the invasion of general microorganisms other than wood-rotting fungi and also against enzymatic digestion of cellulose. We assumed that white-rot fungi first attack the lignin-carbohydrate complex (LCC) and then decompose to some degree into oligomers of lignin and hemicellulose by an unknown enzymatic reaction. The study began with a screening of the fungus, which grew well on the LCC medium. LCCs were prepared from wood meal ofPicea jezoensis that had been extracted MWL, by the method of Koshijima (1). Six fungi (2) that grew well on the media containing decayed lignin were inoculated on agar media of LCC. After 3 d cultivation, the fungiGanoderma sp. andPoria subacida showed most growth on the medium. Crude enzyme preparations were made from decayed wood meal media with each fungus. Chromatographic detection of decomposed compounds from LCC, which is soluble in hot water, by each enzyme and Meicelase fromTricoderma viride, suggest that the wood-rotting fungus may contain another enzyme able to liberate a phenolic compound from LCC besides the enzymes ofTricoderma viride.     

Enhancing enzymatic hydrolysis of crystalline cellulose and lignocellulose by adding long-chain fatty alcohols

The effects of long-chain fatty alcohols (LFAs) on the enzymatic hydrolysis of crystalline cellulose by two commercial Trichoderma reesei cellulase cocktails (CTec2 and Celluclast 1.5L) were studied. It was found that n-butanol inhibited the enzymatic hydrolysis, but n-octanol, n-decanol and n-dodecanol had strong enhancement on enzymatic hydrolysis of crystalline cellulose in the buffer pH range from 4.0 to 6.0. LFAs can increase the hydrolysis efficiency of crystalline cellulose from 37 to 57 % at Celluclast 1.5L loading of ten filter paper units (FPU)/g glucan. LFAs have similar enhancement on the enzymatic hydrolysis of crystalline cellulose mixed with lignin or xylan. The enhancement of LFAs increased with the decrease of the crystallinity index. LFAs not only enhanced the high-solid enzymatic hydrolysis of lignocellulose, but also improved the rheological properties of high-solid lignocellulosic slurries by decreasing the yield stress and complex viscosity. Meanwhile, LFAs can improve the enzymatic hydrolysis of cellobiose to glucose, especially at low cellulase loading.     

木质素活化及在木材胶粘剂中的应用进展

木质素是相对分子量较高的天然聚合物,由于具有苯酚结构利于制备木材胶粘剂,但是木质素本身反应活性低,一般都将其活化后再利用.而且,除了以往利用最多的造纸工业产生的木质素外,研究发现木材经过褐腐菌降解后残留主要成分是结构部分发生变化的木质素,这种可再生生物质资源以其自身的结构特点在合成胶粘剂上也有很大的优势,本文结合木质素胶粘剂应用中的问题,重点概述了活化木质素的各种方法及褐腐木质素在木材胶粘剂中的应用.     

Inhibition Performance of Lignocellulose Degradation Products on Industrial Cellulase Enzymes During Cellulose Hydrolysis

This study examined the inhibition performance by the major lignocellulose degradation products, including organic acids, furan derivatives, lignin derivatives, and ethanol, on a broadly used commercial cellulase enzyme Spezyme CP (Genencor International, Rochester, NY, USA) to cellulose hydrolysis at both the well-mixing state (shaking flask) and the static state (test tube). The cellulase activity in the cellulase complex of Spezyme CP was assumed to be one single “cellulase”, and the apparent kinetic parameters of this cellulase enzyme were measured as an approximate index of the inhibitory effect to the industrial cellulase enzyme. The inhibition performance of these degradation products was compared and analyzed using the determined apparent kinetic parameters. All the degradation products strongly inhibit the cellulose hydrolysis by cellulase enzyme, and the inhibitions on cellulase were all competitive type. The order of the inhibition strength by the lignocellulose degradation products to cellulase is lignin derivatives > furan derivatives > organic acids > ethanol. This study gave a quantitative view to the enzymatic hydrolysis of lignocellulose under the inhibition performance of the lignocellulose degradation products and will help to understand the lignocellulose recalcitrance to enzyme hydrolysis.     

化学改性对木材热塑性能的影响

在非有机溶剂体系中对木粉进行酯化和接枝处理,能够降低纤维素结晶度,破坏木素的化学结合,处理后的木粉的热软化温度比未处理木粉低,虽然不能完全塑化,但在160℃的温度下热压成型可以得到表面光滑,红褐色的半透明压片,表面化学处理已赋予木材一定的热压加工性能。     

Heterologous Expression and Characterization of a Glycoside Hydrolase Family 45 endo-β-1,4-Glucanase from a Symbiotic Protist of the Lower Termite, Reticulitermes speratus

The termite symbiotic system is one of the efficient lignocellulose degradation systems. We tried to express and characterize a novel cellulolytic enzyme from this system. Here, we report the isolation of an endo-β-1,4-glucanase gene homolog of glycoside hydrolase family 45 from a symbiotic protistan community of Reticulitermes speratus. Heterologous expression of this gene was performed using the expression system of Aspergillus oryzae. Analysis of enzymatic properties revealed 786 μmol/min/mg protein in specific activity, a V _max of 833.0 units/mg protein, and a K _m value of 2.58 mg/ml with carboxymethyl cellulose as the substrate. Thin-layer chromatography analysis showed that RsSymEG2 produces cellobiose from cellodextrins larger than cellohexaose. This enzyme showed high specific activity like other endo-β-1,4-glucanases from the symbiotic system of termites. It means that the termite symbiotic system is a good resource for highly active endo-β-1,4-glucanases.     

Variations in some extracellular enzyme activities during degradation of lignocellulose byPhanerochaete chrysosporium

The white-rot fungusPhanerochaete chrysosporium is able to degrade lignin only when its primary growth phase is completed. We have recently shown that the organism is able to establish new growth at 10–15 d intervals by recycling its own nitrogen (2). We have now further characterized this growth-rest cycle by measuring changes in extracellular protease, cellulase, and xylanase activities together with total extracellular protein during growth on different carbon sources.

1. WhenP. chrysosporium is grown on a N-limited glucose medium, the cessation of primary growth is closely connected to the increase in extracellular proteolytic activity. When the culture is not O₂-limited (2) it becomes ligninolytically active after about 2 d with a simultaneous decrease in proteolytic activity and an increase in extracellular protein. In O₂-limited cultures, the proteolytic activity remains on a high level for up to 6–7 d. During the second growth phase, the proteolytic activity again increases.
2. When P.chrysosporium is grown on a N-limited glucose medium supplemented with lignocellulosic materials the cellulase and xylanase activities are suppressed and the growth is again connected to an increase in extracellular proteolytic activity. Lignin is not degraded during the growth phases.
3. When P.chrysosporium is grown on a N-limited medium with lignocellulose as the only energy source, the growth phases are connected with increased cellulolytic, xylanolytic, and proteolytic activities. Again during the growth phase, lignin is not degraded. During the ligninolytic phase the level of measured extracellular enzyme activities decreases. A simultaneous increase in total extracellular protein seems to indicate that these enzymes are partly reused for synthesis of the ligninolytic system. Proteins associated with the ligninolytic system appear to be partly reused to synthesize the hydrolytic enzymes for the next growth phase.

     

Lignin biotransformations by an aromatic aldehyde oxidase produced byStreptomyces viridosporus T7A

Streptomyces viridosporus produces an intracellular aromatic aldehyde oxidase that oxidizes aromatic and α, β-unsaturated aromatic aldehydes to their corresponding acids. It also produces extracellular oxidase as shown by zones of clearing when grown on agar containing insoluble dehydrodivanillin (DHDV). This extracellular form may be responsible for oxidizing aldehyde groups in lignin. The extracellular oxidase was expressed maximally after 3 d growth in medium containing only yeast extract. However, higher levels were produced when lignocellulose was in the medium. The enzyme was partially purified and its molecular weight was approximated to be about 80,000 daltons. Mutant cultures that had lost the ability to produce zones of clearing on DHDV-containing agar solubilized smaller quantities of lignin as compared to the wild type, except for one strain. A partially purified oxidase preparation was shown to oxidize a natural lignocellulose substrate.     

Lignified materials as potential medicinal resources. III. Diversity of biological activity and possible molecular species involved

Diverse biological activities of hot-water and alkali extracts of lignified materials were reviewed and the molecular species involved are discussed. Materials tested included pine cone of Pinus parviflora SIEB. et Zucc., wood chips of slash pine, Douglas fir, and tallow wood, and two basidiocarps, in addition to their partially degraded preparations and commercial lignins. As a tentative conclusion, the lignin structure of these extracts might be responsible for the potent stimulation of granulocytic cell iodination, inhibition of viral infection and/or proliferation in vitro, and inactivation of viral ribonucleic acid (RNA)-dependent RNA polymerase and (adenosine diphosphate-ribose)n glycohydrolase. Other activities displayed by some of these extracts, such as antibacterial and antitumor activities, induction of hemolytic plaque-forming-cells in mice, and stimulation of deoxyribonucleic acid synthesis of isolated splenocytes, remain to be investigated.     

Graft polymerization of monomers onto cellulose and lignocelluloses by chemically induced initiator

The presence of a low percentage of lignin retards and inhibits the graft polymerization reaction of some vinyl monomers on lignocellulosic substrates. The retardation or inhibition effects of lignin in situ are discussed.     

Microbial attack on lignocellulose in the rumen

The microbial population of the rumen consists of many types and species of anaerobic and facultatively anaerobic microorganisms, often at high population densities, living in symbiosis with the animal. The animal is unable to synthesize enzymes capable of digesting the major structural components of plant cell walls (fiber) and relies on the rumen microbes to ferment this material with the generation of volatile fatty acids and microbial cells that the animal can utilize. The crude fiber fraction of ruminant forages consists mainly of cellulose, hemicellulose, and lignin. The rumen contents are rich in organic matter, which has a pH of 5.5–6.9, is maintained at about 39‡C, and has a low redox potential with little free oxygen in the rumen liquor. When plant material enters the rumen, it is invaded by many species of microorganisms, some of which digest certain structural components of the plant cell walls. Measurable digestion of plant cell walls occurs 4–5 h after ingestion by the animal. The rate and extent of digestion is affected by many factors, including the nature and degree of adaptation of the microbial population to the diet, the species of plant and its lignin content, the form in which it is presented to the animal, the amount consumed, and the rate of passage through the rumen. Because the rumen contents are anoxic, there is little degradation of lignin. Some solubilization occurs and lignin-hemicellulose complexes are found in rumen liquor, probably released by cellulolytic and hemicellulolytic microorganisms. One species of bacterium isolated from the rumen preferentially attacked highly lignified cell walls and grew on phenolic acids both aerobically and anaerobically (Akin, 1980), but the abundance and distribution of the species is not known. Phenolic acids are also released and further metabolized in the rumen, and methoxyal groups removed from lignin. Since lignin is covalently bound to cellulose and hemicellulose in the plant cell wall, it probably protects these polysaccharides from microbial attack both physically and chemically. Delignification increases the digestibility of cell wall polysaccharides several-fold. Cellulose may also be shielded from microbial attack by encrusting xylan or xyloglucans (Albersheim, 1975). When plant tissues enter the rumen, they are invaded by both cellulolytic and noncellulolytic microorganisms. Initial invasion is by ciliate protozoa and motile bacteria, followed by phycomycete zoospores and, later, nonmotile bacteria, including cellulolytic species. Some species of ciliate protozoa (e.g.,Epidinium ecaudatum) immediately commence to digest the plant cell walls, but cellulolysis by phycomycete fungi and bacteria is delayed because of preferential metabolism of soluble carbohydrates and the lag before significant attachment of cellulolytic bacteria has occurred. In the predominant cellulolytic rumen bacteria,Ruminococcus albus, R. flavefasciens, andBacteroides succinogenes (Forsberg et al., 1981), adhesion is a prerequisite to cellulolysis because the cellulase enzymes are bound to the cell surface, but some strains ofB. succinogenes also release vesicle-bound enzymes. Cellulases in some species of protozoa (e.g.,Epidinium ecaudatum,Eudiplodinium maggii, andEremoplastron bovis) are now considered to be of protozoon origin (Coleman et al., 1976), but ingested bacteria and adsorbed enzymes may contribute to protozoon cellulolysis. All species of rumen phycomycete fungi examined (Orpin, 1981) have been shown to be cellulolytic and grow on plant cell walls. The cellulase produced by one strain ofNeocallimastix frontalis was associated in part with membranous vesicles released into the medium. Digestion of plant cell walls by the phycomycete fungi is accompanied by the loss of up to 20% of the lignin as a ligninhemicellulose complex. The enzymology of cellulolysis in the rumen is not completely known. It is clear that more than one enzyme is responsible for complete hydrolyses of cellulose to glucose or cellobiose, and endo-1,4-Β-glucanases and Β-1,4-glucosidases have been found in several species of rumen microorganisms. There is also evidence for a ‘swelling factor’ being necessary prior to cellulolysis by some rumen species. All of the cellulolytic rumen microorganisms can also attack, to some degree, the hemicelluloses of the plant cell walls. In some species, cellulase and xylanase activity is associated with the same enzyme complex (e.g.,Bacteroides succinogenes). Other bacteria may attack hemicelluloses, but not cellulose (e.g., some strains ofButyrivibrio fibrisolvens), and others (e.g.,Lachnospira multiparus) digest pectin which allows plant cells to separate and make more cell wall components available to microbial attack. All these organisms act in a consortium resulting in extensive digestion of the plant cell walls.     

Enzymes involved in cellulose and lignin degradation

A detailed presentation was given of the discovered and studied enzymes involved in degradation of cellulose and lignin by the white-rot fungus,Sporotrichum pulverulentum (Phanerochaete chrysosporium). The fungus utilizes, for the degradation of cellulose: (a) Five different endo-1,4-Β-glucanases (b) One exo-1,4-Β-glucanase (acting synergistically with the endoglucanases) (c) Two 1,4-Β-glucosidases The regulation, induction, and catabolite repression of the endoglucanases have been studied in depth and the results of these studies were also presented. In addition to the hydrolytic enzymes,S. pulverulentum also produces the oxidative enzyme cellobiose oxidase that is of importance for cellulose degradation. Another unconventional enzyme is cellobiose: quinone oxidoreductase, which is of importance for both cellulose and lignin degradation. It reduces quinones from the lignin under oxidation of cellobiose from the cellulose. It has recently been discovered thatS. pulverulentum produces two acidic proteases of importance for cellulose degradation since they enhance the endoglucanase activity, particularly in young cultures of the fungus grown on cellulose. The enzymes involved in lignin degradation are not known nearly as well as these involved in cellulose degradation. However, extracellular phenol oxidases, laccase, and peroxidase have been shown to be involved in and necessary for lignin degradation to take place. A phenol oxidase-less mutant ofS. pulverulentum cannot degrade lignin unless a phenol oxidase is added to the medium. Recently, an enzyme splitting the α—Β bond in the propane side chain has been discovered by Kirk and coworkers. Several enzymes involved in the metabolism of vanillic acid, always a metabolite in lignin degradation, have been discovered and studied in our laboratory. Presentations of the enzymes for decarboxylation, demethoxylation, methanol oxidation, ring cleavage, and intracellular quinone reduction by NAD(P)H: quinone oxidoreductase were given. A discussion of possibilities for a specific enzymic primary attack on the native lignin, as well as of the likeliness for an unspecific radical nature of this attack, was also given.     

Effect and Modeling of Glucose Inhibition and In Situ Glucose Removal During Enzymatic Hydrolysis of Pretreated Wheat Straw

The enzymatic hydrolysis of lignocellulosic biomass is known to be product-inhibited by glucose. In this study, the effects on cellulolytic glucose yields of glucose inhibition and in situ glucose removal were examined and modeled during extended treatment of heat-pretreated wheat straw with the cellulolytic enzyme system, Celluclast? 1.5 L, from Trichoderma reesei, supplemented with a β-glucosidase, Novozym? 188, from Aspergillus niger. Addition of glucose (0–40 g/L) significantly decreased the enzyme-catalyzed glucose formation rates and final glucose yields, in a dose-dependent manner, during 96 h of reaction. When glucose was removed by dialysis during the enzymatic hydrolysis, the cellulose conversion rates and glucose yields increased. In fact, with dialytic in situ glucose removal, the rate of enzyme-catalyzed glucose release during 48–72 h of reaction recovered from 20–40% to become ≈70% of the rate recorded during 6–24 h of reaction. Although Michaelis–Menten kinetics do not suffice to model the kinetics of the complex multi-enzymatic degradation of cellulose, the data for the glucose inhibition were surprisingly well described by simple Michaelis–Menten inhibition models without great significance of the inhibition mechanism. Moreover, the experimental in situ removal of glucose could be simulated by a Michaelis–Menten inhibition model. The data provide an important base for design of novel reactors and operating regimes which include continuous product removal during enzymatic hydrolysis of lignocellulose.     

Assessment of pretreatment conditions to obtain fast complete hydrolysis on high substrate concentrations

Steam-heating of aspen wood chips improved the enzymatic digestibility of the cellulose. Scaling up the reaction vessel from 2 to 60 L had virtually no influence on the chemical composition and the accessibility of the lignocellulosic substrate. Over 85% of the cellulose could be hydrolyzed to glucose when an 8% substrate concentration was used. The residual content of alkali-insoluble lignin appeared to control the digestibility of the cellulose. Increased delignification either by prolonged steaming, oxidative posttreatment, or SO₂ catalysis improved the accessibility of the cellulose. The use of SO₂ as a catalyst also increased the recovery yield of the wood after steam-heating, with more than 70% of the original xylan recovered as monomeric xylose. Conversion yields of above 90% were achieved at low levels of filter paper activity after a relatively short incubation time. Removal of alkali-soluble lignin did not influence digestibility when the enzyme concentration was based on the cellulose content of the substrates.     

Cotton Stalk Pretreatment Using <Emphasis Type="Italic">Daedalea flavida</Emphasis>, <Emphasis Type="Italic">Phlebia radiata</Emphasis>, and <Emphasis Type="Italic">Flavodon flavus</Emphasis>: Lignin Degradation,Cellulose Recovery,and Enzymatic Saccharification

Lignocellulolytic enzyme activities of selective fungi Daedalea flavida MTCC 145 (DF-2), Phlebia radiata MTCC 2791 (PR), and non-selective fungus Flavodon flavus MTCC 168 (FF) were studied for pretreatment of cotton stalks. Simultaneous productions of high LiP and laccase activities by DF-2 during early phase of growth were effective for lignin degradation 27.83 ± 1.25 % (w/w of lignin) in 20-day pretreatment. Production of high MnP activity without laccase in the early growth phase of PR was ineffective and delayed lignin degradation 24.93 ± 1.53 % in 25 days due to laccase production at later phase. With no LiP activity, low activities of MnP and laccase by FF yielded poor lignin degradation 15.09 ± 0.6 % in 20 days. Xylanase was predominant cellulolytic enzyme produced by DF-2, resulting hemicellulose as main carbon and energy source with 83 % of cellulose recovery after 40 days of pretreatment. The glucose yield improved more than two fold from 20-day DF-2 pretreated cotton stalks after enzymatic saccharification.     

Enhanced deconstruction and dissolution of lignocellulosic biomass in ionic liquid at high water content by lithium chloride

Fabricating an aqueous ionic liquid (IL) for deconstruction and dissolution of lignocellulose is attractive because addition of water could reduce the cost and viscosity of the solvent and improve the biomass processing, but the solvating power of the IL is usually depressed in the presence of water. In the present study, an aqueous IL consisting of 1-butyl-3-methylimidazolium chloride (BmimCl), water, and lithium chloride was fabricated for efficient deconstruction and dissolution of lignocellulose (bamboo). The dissolution of cell wall components (cellulose, lignin, and hemicelluloses) in the aqueous IL was investigated. The results indicated that the presence of water significantly reduced the solvating power of BmimCl; For example, 11.5 % water decreased the dissolution of bamboo in BmimCl from ~97 to ~53 %. Dissolution of cellulose and lignin was specifically depressed. However, addition of lithium chloride was able to improve the tolerance of BmimCl to water and enhance the deconstruction and dissolution of biomass in BmimCl with high water content. It was found that approximately 80 % bamboo could be dissolved in solvent consisting of 45 wt% BmimCl and 55 wt% LiCl·2H₂O (25 wt% overall water content in the solvent). In particular, lignin and hemicelluloses were selectively dissolved by 96 and 92 %, respectively. The undissolved residue was predominantly composed of cellulose (~86 %) with a small amount of lignin (<5 %). BmimCl-LiCl-H₂O is a promising and effective solvent system with low cost and viscosity for biomass processing.     

Influence of lignocellulose-derived aromatic compounds on oxygen-limited growth and ethanolic fermentation by Saccharomyces cerevisiae

Phenolic compounds released and generated during hydrolysis inhibit fermentation of lignocellulose hydrolysates to ethanol by Saccharomyces cerevisiae. A wide variety of aromatic compounds form from lignin, which is partially degraded during acid hydrolysis of the lignocellulosic raw material. Aromatic compounds may also form as a result of sugar degradation and dare present in wood as extractives. The influence of hydroxy-methoxy-benzaldehydes, diphenols/quinones, and phenylpropane derivatives on S. cerevisiae cell growth and ethanol formation was assayed using a defined medium and oxygen-limited conditions. The inhibition effected by the hydroxy-methoxy-benzaldehydes was highly dependent on the positions of the substituents. A major difference in inhibition by the oxidized and reduced form of a diphenol/quinone was observed, the oxidized form being the more inhibitory. The phenylpropane derivatives were examined with respect to difference in toxicity depending on the oxidation-reduction state of the γ-carbon, the presence and position of unsaturated bonds in the aliphatic side chain, and the number and identity of hydroxyl and methoxyl substituents. Transformations of aromatic compounds occuring during the fermentation included aldehyde reduction, quinone reduction, and double bond saturation. Aromatic alcohols were detected as products of reductions of the corresponding aldehydes, namely hydroxy-methoxy-benzaldehydes and coniferyl aldehyde. High molecular mass compounds and the corresponding diphenol were detected as products of quinone reduction. Together with coniferyl alcohol, dihydroconiferyl alcohol was identified as a major transformation products of conifery aldehyde.

     

Effect of Gel Structure on the In Vitro Gastrointestinal Digestion Behaviour of Whey Protein Emulsion Gels and the Bioaccessibility of Capsaicinoids

This study investigated the effect of gel structure on the digestion of heat-set whey protein emulsion gels containing capsaicinoids (CAP), including the bioaccessibility of CAP. Upon heat treatment at 90 °C, whey protein emulsion gels containing CAP (10 wt% whey protein isolate, 20 wt% soybean oil, 0.02 wt% CAP) with different structures and gel mechanical strengths were formed by varying ionic strength. The hard gel (i.e., oil droplet size d_4,3 ~ 0.5 μm, 200 mM NaCl), with compact particulate gel structure, led to slower disintegration of the gel particles and slower hydrolysis of the whey proteins during gastric digestion compared with the soft gel (i.e., d_4,3 ~ 0.5 μm, 10 mM NaCl). The oil droplets started to coalesce after 60 min of gastric digestion in the soft gel, whereas minor oil droplet coalescence was observed for the hard gel at the end of the gastric digestion. In general, during intestinal digestion, the gastric digesta from the hard gel was disintegrated more slowly than that from the soft gel. A power-law fit between the bioaccessibility of CAP (Y) and the extent of lipid digestion (X) was established: Y = 49.2 × (X − 305.3)^0.104, with R² = 0.84. A greater extent of lipid digestion would lead to greater release of CAP from the food matrix; also, more lipolytic products would be produced and would participate in micelle formation, which would help to solubilize the released CAP and therefore result in their higher bioaccessibility.     

Response of Cellulase Activity in pH-Controlled Cultures of the Filamentous Fungus <Emphasis Type="Italic">Acremonium cellulolyticus</Emphasis>

Cellulase production was investigated in pH-controlled cultures of Acremonium cellulolyticus. The response to culture pH was investigated for three cellulolytic enzymes, carbomethyl cellulase (CMCase), avicelase, and β-glucosidase. Avicelase and β-glucosidase showed similar profiles, with maximum activity in cultures at pH 5.5–6. The CMCase activity was highest in a pH 4 culture. At an acidic pH, the ratios of CMCase and avicelase activity to cellulase activity defined by filter paper unit were high, but at a neutral pH, the β-glucosidase ratio was high. The pH 6.0 culture showed the highest cellulase activity within the range of pH 3.5–6.5 cultures. The saccharification activity from A. cellulolyticus was compared to those of the cellulolytic enzymes from other species. The A. cellulolyticus culture broth had a saccharification yield comparable to those of the Trichoderma enzymes GC220 and Cellulosin T2, under conditions with the same cellulase activity. The saccharification yields from Solka floc, Avicel, and waste paper, measured as the percent of released reducing sugar to dried substrate, were greater than 80% after 96 h of reaction. The yields were 16% from carboxymethylcellulose and 26% from wood chip refiner. Thus, the A. cellulolyticus enzymes were suitable for converting cellulolytic biomass to reducing sugars for biomass ethanol production. This study is a step toward the establishment of an efficient system to reutilize cellulolytic biomass.