The objective of this experiment was to determine the respective effects of level of intake and of the amount of volatile fatty acids (VFAs) present in the rumen on VFA ruminal absorption. In a factorial design, six ewes received a hay diet either at 126 or at 73% of energy maintenance requirements. Their capacity of absorption of VFAs was evaluated by the method of temporarily isolated rumens,...

I. Examination of the digesta from all regions of the avian digestive tract showed that volatile fatty acids (VFAs) were present in greatest concentration in the caeca and that they comprised mainly acetic, propionic and butyric acids. 2. All droppings contained VFAs but they were present in highest concentration in those of caecal origin. Caecectomy was followed by a marked reduction in the to...

The use of volatile fatty acids (VFAs) for microbial lipid accumulation was investigated in flask cultures of Cryptococcus albidus. The optimum culture temperature and pH were 25°C and pH 6.0, respectively, and the highest lipid content (27.8%) was obtained with ammonia chloride as a nitrogen source. The lipid yield coefficient on VFAs was 0.167 g/g of C. albidus with a VFAs (acetic, propionic,...

A consecutive-reaction kinetic model for the sucrose-fed upflow anaerobic sludge bed (UASB) reactor that accounts for a layered structure of the granule and the mass fraction of methanogens (f) is proposed. When the UASB reactor was maintained at the volumetric loading rates (VLR) of 7.9-13.8 kg chemical oxygen demand (COD)/m(3) d, the accumulated volatile fatty acids (VFAs) increased with incr...

Cost effective production of biofuels depends critically on feedstock cost and availability. As such, volatile fatty acids (VFAs) can play an important role in advancing sustainable biofuel production since they can be derived from low cost feedstock including gases and municipal solid waste. To this end, we studied fermentations of the oleaginous microbe Yarrowia lipolytica engineered for lipi...

Two classes of nominal automata, namely Usage Automata (UAs) and Variable Finite Automata (VFAs) are considered to express resource control policies over program execution traces expressed by a nominal calculus (Usages). We first analyse closure properties of UAs, and then show UAs less expressive than VFAs. We finally carry over to VFAs the symbolic technique for model checking Usages against ...

The combined fermentation of sludge from the secondary sedimentation tank of municipal wastewater treatment plants and food waste enables not only waste reduction, but also the acquisition of volatile fatty acids (VFAs) for the biosynthesis of polyhydroxyalkanoates (PHAs). To better understand variables influencing the production of VFAs and PHAs, this study considered anaerobic fermentation of...

Volatile fatty acids (VFAs) are a group of common metabolites and semiochemicals mediating information transfer between higher organisms and bacteria, either from microbiome or external environment. VFAs commonly occur among various insect orders. There are numerous studies exploring their influence on the behavior of different insect species. In relation to the papers published by J. E. McFarl...

We describe a procedure for preparing fecal samples for determination of volatile fatty acids (VFAs) by gas-liquid chromatography (GLC) and "high-performance" liquid chromatography (HPLC). The simple, one-step procedure involves only ultrafiltration through a membrane with a molecular-mass cutoff of 3000 Da. As revealed by the GLC chromatograms, ultrafiltration appears to be as effective as ste...

Volatile fatty acids (VFA) are short chain aliphatic monocarboxylic acids containing from 2 to 8 carbon atoms in a molecule. They are formed in the process of anaerobic biodegradation of larger organic molecules and therefore are commonly present in municipal wastewater, effluents of food industry, livestock farm wastewater, sewage sludge, landfill leachate, feces, urine, etc. and are emitted b...