Production of cellulase by Trichoderma.

The cellulase complex in T. viride is inducible. For large-scale enzyme production the fungus should be cultured on media containing cellulose. The cellulase enzymes are respressible. To produce and maintain best cellulase yields cultural conditions which lead to carbohydrate consumption in excess of cellular needs should be avoided. With the present mutant (QM9414) extracellular enzyme preparations having 1.6 FP units/ml and 1.6 mg protein/ml have been obtained within four to five days in submerged fermentation. Such preparations are capable of producing a 5% sugar solution when mixed with 10% ball milled cellulose and incubated 24 hr at 50 degrees C. Further improvements of cellulase yields are being sought by continued mutagenesis and increased nutrient levels in the growth medium.     

Production of levanase byRhodotorula sp.

Rhodotorula sp. produced a high yield of levanase (12.5 nkat/mL) in shake flasks in basal medium containing 1% maltose as the sole carbon source. Among the different carbon sources used, maltose was found to be the best for levanase production. The optimum temperature and pH for levanase production were 30°C and 6, respectively. In a batch reactor the enzyme productivity was higher (500 nkat L⁻¹ h⁻¹) than in shaken flasks (347 nkat L⁻¹ h⁻¹).     

Production of laccase byCurvularia sp.

ACurvularia sp. isolated from soil was found to contain laccase activity toward guaiacol as substrate. The organism produced an extracellular laccase in a medium containing yeast extract, peptone and dextrose. Initial medium pH 4.0 and cultivation temperature 30°C were found to be most suitable for maximum enzyme production. The optimum pH and temperature for laccase activity were found to be 5.2 and 50°C, respectively. Under optimum conditions, the enzyme had aK _m (guaiacol) of 0.75 mmol/L and aV of 1.50 CU min⁻¹ ml⁻¹. Some divalent metal ions inhibited laccase activity at very low concentrations.     

Production of L-serine by Sarcina albida.

Conditions for the production of microbial L-serine hydroxymethyltransferase and for the conversion of glycine to L-serine were studied. A number of microorganisms were screened for their abilities to form and accululate L-serine from glycine, and Sarcina albida was selected as the best organism. Enzyme activity in this organism as high as 0.12 U/ml could be produced in shaken cultures at 30 degrees C in a medium containing glucose, ammonium sulfate, glycine, yeast extract, and inorganic salts. L-Serine was produced most efficiently by shaking cells at 30 degrees C in a reaction mixture containing 20% glycine, 5 X 10(-3) M formaldehyde, and 3 X 10(-4) M pyridoxal phosphate in yields of 22 mg of broth in 5 days. L-Serine was easily isolated in 84% yields by ion-exchange resin.     

Production of rats in synchronised batches.

Successful synchronisation of copulations and births for the 1st parity permit continued synchrony of parturitions in subsequent parities. Foetal implantation after post-partum copulation was delayed by multiples of the oestrous cycle; both season and number of sucking neonates influenced the time of implantation. Post-weaning matings gave a high conception rate with a parturition spread of 36 hours for 94% of the original group.     

Production of L-serine by Sarcina albida.

Conditions for the production of microbial L-serine hydroxymethyltransferase and for the conversion of glycine to L-serine were studied. A number of microorganisms were screened for their abilities to form and accululate L-serine from glycine, and Sarcina albida was selected as the best organism. Enzyme activity in this organism as high as 0.12 U/ml could be produced in shaken cultures at 30 degrees C in a medium containing glucose, ammonium sulfate, glycine, yeast extract, and inorganic salts. L-Serine was produced most efficiently by shaking cells at 30 degrees C in a reaction mixture containing 20% glycine, 5 X 10(-3) M formaldehyde, and 3 X 10(-4) M pyridoxal phosphate in yields of 22 mg of broth in 5 days. L-Serine was easily isolated in 84% yields by ion-exchange resin.     

Production of food and fodder yeasts.

A decade or so ago, there was considerable interest in developing single cell protein production from raw materials. Many factors have influenced the development of fodder yeast technology, notably the biochemistry and physiology of the yeast. It is shown that those considerations have led to the choice of a continuous fermentation technology.     

Production of cellulases by Thermomonospora sp.

Glucose, cellulose, Avicel, and Solka Floc were utilized as substrates for growth of Thermomonospora sp in order to study the induction–repression characteristics of its associated cellulase system. While glucose proved to be an effective repressor of the cellulase enzymes, the other three substrates induced relatively high levels of enzyme activity as measured by the filter paper assay. On a unit cell mass basis the highest values of cellulase activity were obtained when Avicel was utilized as the carbon and energy source. The nature of the cellulosic material and its initial concentration were identified as two very important parameters of the induction process.     

Production of calcium gluconate by fermentation.

Calcium gluconate production by Aspergillus niger was investigated in shake flask, rolling shaker, air-lift reactor and stirred reactor. Growth pattern of the organism and fermentation conditions determined the yield of the product. High calcium gluconate production was achieved in air-lift reactor with pellet form of cell growth at moderate specific growth rate and biomass concentration. In another variation of air-lift reactor, when calcium carbonate was confined to a cellulose membrane, calcium gluconate production was maximum (149 g/L). At higher specific growth rate, obtained in shake flask, despite the formation of cell pellets, product formation was low. Physical separation of particulate calcium carbonate and growing cells favoured product formation. In stirred reactor pulpy mycelial growth was obtained and calcium gluconate production was poor.     

Production of antibody against ochratoxin A.

Antibody against ochratoxin A was obtained after repeated injection of different protein-ochratoxin A conjugates to rabbits. Among many protein-ochratoxin conjugates tested, bovine serum albumin-ochratoxin A was found to be the best antigen. The antibody is specific for ochratoxins A, C, and T, but is not specific for ochratoxins B, alpha, and other coumarin derivatives. The sensitivity for ochratoxin A detection using a binding assay is in the range of 0.5 to 10 ng/0.5-ml sample. Detailed methods for the preparation of protein-ochratoxin conjugates, preparation of immune serum, and methods for antibody titers are described.     

Production of platelet-activating factor in slugs.

The land slug, Incilaria bilineata, was shown to contain a large amount of 1-O-alkyl-2-acyl (long chain)-sn-glycero-3-phosphocholine, which accounts for as much as 47% of the choline glycerophospholipid fraction. Since this unique either phospholipid has been regarded as a stored precursor form of platelet-activating factor (PAF) in mammalian inflammatory cells, we examined the possibility of the presence of PAF in this animal. We obtained the evidence for the occurrence of significant amounts of PAF in two species of slugs, Incilaria bilineta and Incilaria fruhstorferi. Gas chromatography-mass spectrometry analysis revealed that the alkyl fatty chain of PAF principally consists of 16:0. We confirmed the presence of both enzyme activities catalyzing the formation of PAF, one for the remodeling pathway and the other for the de novo pathway. We also found the occurrence of other enzyme activities involved in PAF metabolism: acetylhydrolase activity which inactivates PAF and phospholipase A2 activity toward alkylacylglycerophosphocholine. However, we failed to detect cofactor-independent transacylation activity in this animal. The amounts of PAF in slugs were markedly increased when slugs were administered several treatments which are considered to induce shock, such as the injection of dimethyl sulfoxide or injuries. These results suggest that PAF is produced and may have certain physiological and pathological roles in the land slug, as in the case of mammals.     

农业生产的生态管理

一、引言自50年代起,我国开始从传统农业向现代常规农业转变。随着这一转变的深化,农业生产力水平有了迅速的提高。然而,迅速增长的人口压力,使我国农业一直面临着一些严峻的问题。众多的人口,使我国人均自然资源占有量处于极低的水平。土地资源、水资源及矿产资源的短缺,已成为我国农业发展的基本限制