Effects Of Phenolic Monomers Research Articles

Effects of phenolic monomers on growth of Acidothermus cellulolyticus

Previous studies on biological pretreatment of switchgrass by solid-state fermentation with Acidothermus cellulolyticus 11B have shown that inhibitory compounds prevent growth on untreated switchgrass. A. cellulolyticus was grown in liquid medium containing cellobiose with phenolic monomers added to determine if the phenolic compounds are one possible source of inhibition. Cinnamic acid derivatives (trans-p-coumaric, trans-ferulic, and hydrocinnamic acids), hydroxybenzoic acids (p-hydroxybenzoic, syringic, and vanillic acids), benzaldehydes (vanillin and p-hydroxybenzaldehyde), and condensed tannin monomers (catechin and epicatechin) were tested at levels up to 20 mM. All compounds exhibited a dose-response relationship and strongly inhibited growth at 20 mM. trans-p-Coumaric acid was found to be the strongest inhibitor of A. cellulolyticus growth, with a specific growth rate of 0.004 h(-1) at 1 mM (0.18 h(-1) without phenolic monomer). GC-MS and HPLC methods were used to confirm the presence of these phenolic compounds in switchgrass and measure the amounts extracted using different conditions. The amounts of phenolic compounds measured were found to be higher than the threshold for growth inhibition. Leaching with water at 55°C was inefficient at removing bound phenolics, whereas NaOH treatment improved efficiency. Phenolic compounds spiked into alkaline pretreated switchgrass were also found to inhibit growth of A. cellulolyticus in solid-state fermentation. However, addition of insoluble polyvinylpolypyrrolidone (PVPP) to switchgrass improved growth of A. cellulolyticus in liquid cultures, providing a possible approach for alleviating microbial inhibition due to phenolic compounds in lignocellulose.

Effects of Phenolic Monomers on the Degradation of 14C-Cellulose by Rumen Fungi

Effects of Phenolic Monomers on the Degradation of 14C-Cellulose by Rumen Fungi

Effects of phenolic monomers on the enzymes activities and volatile fatty acids production of Neocallimastix frontalis B9

The effects of phenolic monomers (i.e. ρ-coumaric acid, ferulic acid, ρ-hydroxybenzaldehyde and vanillin) on the enzymes and fermentation activities of Neocallimastix frontalis B9 grown in ball-milled filter paper and guinea grass media were studied. The enzymes studied were carboxymethylcellulase (CMCase), filterpaperase (FPase), xylanase and β-glucosidase. At 96 h of incubation, N. frontalis grown in ball-milled filter paper medium produced comparable xylanase and CMCase activities (0.41, 0.5 μmol/min/mg protein) while in guinea grass medium, N. frontalis produced higher xylanase activity than that of CMCase activity (2.35, 0.05 μmol/min/mg protein). The other enzymes activities were low. When N. frontalis was grown in ball-milled filter paper medium, only acetic acid was produced. However, when grown in guinea grass medium, the major end-product was acetate, but propionic, butyric and isovaleric were also produced in lesser amount. Vanillin showed the least inhibitory effects to enzyme activities of N. frontalis B9 grown in both ball-milled filter paper and guinea grass media. For total volatile fatty acid production, all phenolic monomers showed inhibitory effects, but ρ-coumaric and ferulic acids were the stronger inhibitors than ρ-hydroxybenzaldehyde and vanillin.

Effect of phenolic monomers on biomass and hydrolytic enzyme activities of an anaerobic fungus isolated from wild nil gai (Baselophus tragocamelus).

To test the anaerobic fungus, Piromyces sp. FNG5, for its tolerance to phenolic monomers released in the rumen by degradation of lignocellulosic poor-quality feeds. Effects of phenolic monomers on biomass and fibrolytic enzyme activities of a pure culture of lignocellulolytic anaerobic fungus (Piromyces sp. FNG5) isolated from faeces of wild nil gai (blue bull, Baselophus tragocamelus) were evaluated. There was a reduction in fungal biomass at 1 mm concentration of catechol with complete inhibition at 10 mm. p-Coumaric acid caused a reduction in biomass at 10 mm and no growth was observed above 20 mm concentration. The fungal isolate could tolerate up to 5 mm of ferulic acid without any reduction in biomass level, and was able to grow to some extent up to the highest level of ferulic acid tested (20 mm). Vanillic acid had no effect on biomass of the fungus even up to 50 mm level. The phenolic monomers varied in their potential to inhibit the secretion of carboxymethyl cellulase, xylanase, beta-glucosidase and acetyl esterase activities with catechol being the most inhibitory and vanillic acid being the least inhibitory. After 14 days of incubation, 38.49-65.14%p-Coumaric acid, 65.22-74.10% ferulic acid and 34.13-66.78% vanillic acid disappeared from the medium under anaerobic conditions. It is concluded that the anaerobic fungus Piromyces sp. FNG5 is tolerant to phenolic monomers and has ability to degrade them. Therefore, such anaerobic fungi may play an important role in fibre degradation in the rumen.

Effect of phenolic monomers on the production of laccases by the edible mushroom Pleurotus sajor-caju, and partial characterization of a major laccase component

The effects of several phenolic monomers on the growth and laccase production by the edible mushroom Pleurotus sajor-caju have been compared. Of the phenols tested, 4-hydroxybenzaldehyde and vanillin were most inhibitory to fungal growth, and cultures supplemented with these two compounds also exhibited the largest increases in laccase specific activity compared with unsupplemented controls. Up to five laccase isoforms were detected in culture fluids when P. sajor-caju was grown in submerged culture in the presence of several phenolic monomers. A major laccase component (laccase IV) present in P. sajor-caju culture supernatants was purified 152-fold with an overall recovery of 4.9%. Laccase IV was shown to be homogeneous by SDS-PAGE and isoelectric focusing, and had a molecular weight of 55 kD and an isoelectric point of 3.6. It displayed a maximum reaction velocity at pH 2.1 and 45 C, and the activation energy of the enzyme reaction between 25 and 45 C as determined by an Arrhenius plot was 12.4 kJ mol-1. The Km of laccase IV, as determined using ABTS as the substrate, was 0.092 mM. Laccase IV was glycosylated with mannose as the major sugar component together with galactose, glucosamine and fucose. Comparison of up to thirteen N-terminal amino acids of laccase IV with those of other fungal laccases revealed the highest similarity (85%) with a laccase from Pleurotus ostreatus. Considerable similarity (46–50%) was also observed with laccases from Coriolus versicolor, Pycnoporus cinnabarinus, Phlebia radiata, Coriolus hirsutus and Ceriporiopsis subvermispora but not Agaricus bisporus.

Effect of Phenolic Monomers on the Production of Laccases by the Edible Mushroom Pleurotus sajor-caju, and Partial Characterization of a Major Laccase Component

Effect of Phenolic Monomers on the Production of Laccases by the Edible Mushroom Pleurotus sajor-caju, and Partial Characterization of a Major Laccase Component

Effect of phenolic monomers on the growth and beta-glucosidase activity of Bacteroides ruminicola and on the carboxymethylcellulase, beta-glucosidase, and xylanase activities of Bacteroides succinogenes.

trans-p-Coumaric acid inhibited the growth of Bacteroides ruminicola on both cellobiose and glucose, while trans-ferulic acid and vanillin retarded growth. The phenolic monomers varied in their potential to inhibit the Bacteroides succinogenes beta-glucosidase, carboxymethylcellulase, and xylanase, with p-coumaric acid being the most inhibitory. The B. ruminicola beta-glucosidase was inhibited less than 10% by all three compounds.

Effect of phenolic monomers on ruminal bacteria.

Ruminal bacteria were subjected to a series of phenolic compounds in various concentrations to acquire fundamental information on the influence on growth and the potential limits to forage utilization by phenolic monomers. Ruminococcus albus 7, Ruminococcus flavefaciens FD-1, Butyrivibrio fibrisolvens 49, and Lachnospira multiparus D-32 were tested against 1, 5, and 10 mM concentrations of sinapic acid, syringaldehyde, syringic acid, ferulic acid, vanillin, vanillic acid, p-coumaric acid, p-hydroxybenzaldehyde, p-hydroxybenzoic acid, and hydrocinnamic acid. Responses were variable and dependent on the phenolic compound and microbial species. Compounds especially toxic (i.e., resulting in poor growth, effect on several species, dose-related response) were p-coumaric acid and p-hydroxybenzaldehyde, and adaptation to the toxins did not occur after three 24-h periods. Syringic, p-hydroxybenzoic, and hydrocinnamic acids stimulated growth of all four species and also stimulated filter paper degradation by R. flavefaciens. None of the stimulatory compounds supported microbial growth in the absence of carbohydrates. In vitro dry matter digestibility of cellulose (Solka-Floc) was not stimulated by any of the phenolic compounds (10 mM), but the cinnamic acids and benzoic aldehydes (10 mM) reduced (P less than 0.05) digestion by the mixed population in ruminal fluid. Growth of R. flavefaciens in the presence of p-hydroxybenzoic acid (10 mM) or p-coumaric acid (5 mM) resulted in recognizable alterations in cell ultrastructure. Both phenolics caused a reduction in cell size (P less than 0.05), and p-coumaric acid caused a reduction in capsular size (P less than 0.05) and produced occasional pleomorphic cells.

Effects of Phenolic Monomers on Rat Performance and Metabolism

Phenolic monomers identified in common roughages were included in diets fed to rats both as mixtures, to mimic phenolic composition of roughages, and individually at various levels. Three performance and digestion/metabolism trials were conducted. Dry matter, protein, total carbohydrate, cellulose, and soluble carbohydrate (dextrose plus starch) digestibilities were measured. Urine and fecal samples were analyzed for phenolic monomers in trial 1. Inclusion of phenolic monomers (p-coumaric, ferulic, protocatechuic and salicylic acids, and vanillin) in rat diets resulted in reduced feed intake with a linear trend toward decreased intake with increasing dietary phenolic (p-coumaric and ferulic acids) concentrations. Average daily gain also exhibited a similar negative linear relationship. p-Coumaric and ferulic acids did not differ from one another in their effects, whereas salicylic acid had greater negative effects and vanillin was not different from the phenolic-free control. Some differences in digestibility of individual nutrients were observed, but were small in magnitude and did not correlate well with the altered growth responses. Analysis of urine and feces revealed low recoveries of phenolic monomers, suggesting extensive metabolism of phenolics by rats after intestinal absorption. Potential exists for phenolic monomers to be intake- and growth-depressing agents in both animal and human diets.