Dilute acid hydrolysis of presscakes from silage and grass to recover hemicellulose-derived sugars

Grass and silage presscakes from various types of raw materials were hydrolyzed with dilute acid at moderate conditions to recover hemicellulose-derived sugars. Extracting the material with cold water prior to hydrolysis significantly increased the yield. The poor performance without extraction was due to the high buffer capacity of the material. The best results were obtained with extracted grass and silage from a permanent pasture and extracted clover/grass silage. The highest observed sugar yield was 16.43 g/100 g dry-matter, which represents approximately 25% of the available sugars and 60% of the hemicellulose fraction. Including the soluble sugar oligomers, the yields were even higher (up to 20 g/100 g dry-matter). A statistical experiment design with extracted clover/grass silage was performed to estimate the effects of temperature, time, and dry-matter concentration. Acid and dry-matter concentration had the highest effect on sugar yield, whereas temperature and acid concentration were mainly responsible for forming sugar degradation products. These findings agree with recent kinetic theories. Yields in this experiment were comparable to those of other lignocellulosic materials.

Acetic acid increases stability of silage under aerobic conditions

The effects of various compounds on the aerobic stability of silages were evaluated. It has been observed that inoculation of whole-crop maize with homofermentative lactic acid bacteria leads to silages which have low stability against aerobic deterioration, while inoculation with heterofermentative lactic acid bacteria, such as Lactobacillus brevis or Lactobacillus buchneri, increases stability. Acetic acid has been proven to be the sole substance responsible for the increased aerobic stability, and this acid acts as an inhibitor of spoilage organisms. Therefore, stability increases exponentially with acetic acid concentration. Only butyric acid has a similar effect. Other compounds, like lactic acid, 1,2-propanediol, and 1-propanol, have been shown to have no effect, while fructose and mannitol reduce stability.

Process development and optimisation of lactic acid purification using electrodialysis

Cell free sodium lactate solutions were subjected to purification based on mono- and bi-polar electrodialysis. Lactate concentration in the product stream increased to a maximum of 15% during mono-polar electrodialysis. Stack energy consumption averaged 0.6 kW h kg(-1) lactate transported at current efficiencies in the 90% range. Under optimum feed concentration (125 g l(-1)) and process conditions (auto-current mode with conductivity setpoints of minimum 5 and maximum 40 mS cm(-1)), lactate flux reached 300 g m(-2) h(-1) and water flux were low for mono-polar electrodialysis averaging 0.3 kg H(2)O per M lactate transported. Glucose in the concentrate stream solutions was reduced to < 2 g l(-1). Acetate impurities enriched from about 0.5 g l(-1) in the feed stream to 1.5 g l(-1) in the concentrate stream solutions. After mono-polar electrodialysis, the concentrated sodium lactate solutions were further purified using bi-polar electrodialysis. Water transport during bi-polar electrodialysis reached figures of 0.070 - 0.222 kg H(2)O per M lactate. Free lactic acid concentration reached 16% with lactate flux of up to 300 g m(-2) h(-1). Stack energy consumption ranged from 0.6 to 1 kW h per kg lactate. Under optimised process conditions current efficiency during bi-polar electrodialysis was consistently around 90%. Glucose was further reduced from 2 to <1 g l(-1) in the free lactic acid solution. Acetic acid impurity remained at around 1 g l(-1). Significant reduction in colour and minerals in the product streams was observed during electrodialysis purification.

Thermophilic production of lactic acid using integrated membrane bioreactor systems coupled with monopolar electrodialysis

The thermophilic Bacillus strain BS119 was selected for this study to demonstrate the long term performance of lactic acid production and simultaneous pre-purification. Integrated continuous cell recycle cultivation using ultra-filtration membrane bioreactor (MBR) systems was investigated. The permeate from the MBR was routed to an on-line electrodialysis (ED) to recover, pre-purify and concentrate lactate. The cultivation and ED was operated at 60 degrees C for more than 1,000 h at a pH of 6.5. At lower dilution rate (0.02 h(-1)), lactate concentration reached a maximum of 55 g l(-1) with clearly lower residual glucose levels. At 0.04 h(-1), lactate concentration was significantly lower at 35 g l(-1). Maximal volumetric productivities of 1.38 g l(-1) h(-1) were achieved. Under stable conditions, lactic acid yield on consumed glucose appeared stable at around 80%. It could be demonstrated that the addition of supplements like yeast extract and peptone severely influences product formation. Integration of mono-polar ED with the MBR systems yields lactate solutions with concentrations of up to 115 g l(-1). Because of the low substrate feed concentrations (less than 50 g l(-1)), lactate flux was rather poor, reaching a low maximum of 140 g m(-2) h(-1); nevertheless, stack energy consumption was positive with an average of 0.49 kWh kg(-1) lactate.

Thermophilic lactic acid production on hemicellulose hydrolysate

Lactic acid has many applications. It can be utilised as road-deicing agent, in the food industry or--after polymerisation--as a biodegradable plastic. The use of lignocellulose biomass will significantly increase the competitiveness of lactic acid-based polymers compared to conventional petroleum based plastics. The Institute for Agrobiotechnology in Tulln (IFA-Tulln) developed a process to apply renewable resources as cheap feedstock for production of lactic acid. The utilisation of thermophiles combined with a suitable pretreatment method enables a fermentation under non sterile conditions with detoxified hemicellulosic hydrolysates. This paper presents growth toxicity tests and batch experiments with bagasse hydrolysate, which were conducted to determine the fermentability of thermophilic wild type strains.

The aerobic stability of silages influenced by metabolites of lactic acid bacteria

The stability of silages after opening the silo depends strongly on the products formed by the microorganism flora present during the conservation process. A silage additive developed at IFA-Tulln showed best results on different crops. In the starting phase of silage fermentation, acetic acid was formed by the heterofermentative lactic acid bacteria L. brevis from sugars. In the later stages, L. buchneri converts also lactic acid into acetic acid. Several trials involving different formulations of starters with varying amounts of single homo- and heterofermentative lactic acid bacteria were tested in laboratory and clump silos. Finally, an optimum composition of lactic acid bacteria, which reliably increases aerobic stability of silages and still guaranties highest quality, was evaluated.

Isoelectric focusing in immobilized pH gradients of phosphoglucomutase and esterases from the spiny lobster

A method is described for detecting polymorphisms of cephalothorax and tail homogenates of 25 puerulus staged Panulirus argus in phosphoglucomutase (PGM) and esterases. Isoelectric focusing in immobilized pH gradients was used. In the pH 6.0-8.0 interval for phosphoglucomutase and in the pH 3.5-5.0 and 4.2-4.9 ranges for esterases, both enzymes appeared as polymorphic band patterns. These could be explained by one locus with 2 alleles for phosphoglucomutase and 3 loci with 2, 3 and 4 alleles for esterases. Esterases exhibit a more extensive polymorphism in immobilized pH gradients than in polyacrylamide gel electrophoresis.

[Clinical and bacteriologic effectiveness of ceftazidime in infections with gram-positive pathogens]

From June 1984 to March 1985 an open, multicenter study was carried out to evaluate the efficacy and safety of ceftazidime in the empirical treatment of severe nosocomial infections. 3799 patients treated in 513 clinical care units were included and 3477 were evaluable. The majority was older than 60 years; most patients showed severe underlying diseases and were in a critical condition. The clinical and bacteriological results with various monoinfections due to gram-positive bacteria are presented. Staphylococcus aureus, Streptococcus pneumoniae and other streptococci were the most frequently isolated organisms. 600 patients with infections due to staphylococci were evaluated separately. The clinical success rate with ceftazidime in S. aureus monoinfections was 90.9%, and the bacteriological success rate was 74.9%.

[Cytoarchitecture and histochemical fluorescence studies of the cingulate cortex in the rat]

The cingular cortex of the rat was examined by means of Golgi's rapid impregnation technique, the glyoxylic acid technique for the detection of biogenic amines and a ninhydrin reaction in the octanoic milieu for the detection of GABA. Six interneuron types are described, differing with respects to their dendrite configurations and axon morphology. The noradrenaline innervation shows considerable differences as compared to the dopamine fibre system. GABA-containing neurons of various shapes and sizes are concentrated in the laminae II and III. The findings are discussed in connection with the conception according to the which the Gyrus cinguli as part of the limbic system might play a role in the genesis of psychopathological processes.

[Spiny neurons in the rat caudate-putamen complex]

The neostriatum of adult normal rats and of rats after surgical lesion of MFB was investigated by means of the rapid Golgi impregnation procedure. Evidence was given for the spiny neuron population to be heterogenous. It was possible to demonstrate four neuron types clearly distinguishable with respect to size and shape of the soma, dendritic pattern, and axon morphology. The morphological heterogeneity of the spiny neurons of the caudatus-putamen-complex of the rat presented here is discussed in functional terms (interneuron and efferent neuron nature, resp.).