Substrate Decomposition Rates Research Articles

The conversion of straw into feed by basidiomycetes

1. The solid-state fermentation of straw byPleurotus cornucopiae, Pleurotus sp. Florida, Agrocybe aegerita, andStropbaria rugosoannulata at 22°, 25°, and 30°C during 0–120 days was examined. 2. During the first stage of fungal growth (saprophytic colonization), the quantity of water soluble substances, reducing sugars, and in vitro digestibility of the straw-fungal myeelium mixture decreased. 3. After 20 days, the amount of water soluble substances and reducing sugars increased. Temperature strongly influenced the rate of substrate decomposition, particularly with cultures ofPleurotus cornucopiae andStropharia rugosoannulata. 4. Of the fungal cultures examined,Pleurotus cornucopiae andStropharia rugosoannulata showed the highest rate of straw decomposition and released the greatest amount of metabolic energy from the straw. 5. The heat of combustion of decomposed substrate decreased due to increasing ash content and varying degree of metabolism of cellulose and lignin. 5. The in vitro digestibility of wheat straw was strongly influenced by incubation temperature and increased during fermentation byPleurotus species andStropharia rugosoannulata. 7. Agrocybe aegerita exhibited good properties for production of fruiting bodies, but this species was not satisfactory for the conversion of plant residues to feed.Stropharia rugosoannulata, however, increased the digestibility of straw by 31.6%. 8. Some technical possibilities for using fungi for upgrading waste straw to animal feed are discussed.

Effect of polyelectrolytes on the kinetics of ionic reactions. Part 2.—Decomposition of p-nitrophenyl phosphate in aqueous solutions of polycations

The decomposition of p-nitrophenyl phosphate in solutions containing polyethyleneimine (PEI) or poly(benzyltrimethylammonium chloride)(PVBA-Cl) has been studied. The polyelectrolytes markedly affect the rate of substrate decomposition. PVBA-Cl catalyses the hydrolysis of the substrate at pH > 6 because the substrate/PVBA-Cl interactions facilitate ester bond cleavage. In PEI solutions nucleophilic attack by the free amino groups of the macroion leads to production of substituted p-nitroaniline (pH > 6). The effects of polyelectrolyte concentration and molecular weight are discussed.

Influence of acetyl-β-methylcholine, carbamoylcholine, and bis-pyridinium compounds on the activity of acetylcholinesterase

The decomposition rate of the substrate acetyl-β-methylcholine by AChE in presence of the antagonists TMB 4, ∗ ∗ [1,1′-trimethylene bis-(4-formylpyridinium bromide)] dioxime. toxogonin, † † Obidoxime = [1,1′-oxydimethylene bis-(4-formylpyridinium chloride)] dioxime. and HS 6 ‡ ‡ [l ,I′-oxydimethylene (2-formyl-3-carbamyl-pyridinium chloride)]. was measured in vitro. The results are compared with those of previous studies using acetylcholine as substrate. Furthermore the reactivating potency of toxogonin on the carbamoylcholine-inhibited enzyme was investigated. The antagonists showed different effects on the substrate decomposition rates of the enzyme, depending on the nature of the substrate. It is concluded that the antagonists as well as the substrates react not only with the active centre of AChE but also with a secondary binding site. In the reactivating reaction of carbamoyl-inhibited AChE, a reaction at a secondary binding site is also involved.