Regulatory activity of heterologous gene-activator xlnR of Aspergillus niger in Penicillium canescens

The gene encoding the xlnR xylanolytic activator of the heterologous fungus Aspergillus niger was incorporated into the Penicillium canescens genome. Integration of the xlnR gene resulted in the increase in a number of activities, i.e. endoxylanase, beta-xylosidase, alpha-L-arabinofuranosidase, alpha-galactosidase, and feruloyl esterase, compared to the host P. canescens PCA 10 strain, while beta-galactosidase, beta-glucosidase, endoglucanase, and CMCase activities remained constant. Two different expression constructs were developed. The first consisted of the nucleotide sequence containing the mature P. canescens phytase gene under control of the axhA promoter region gene encoding A. niger (1,4)-beta-D-arabinoxylan-arabinofuranohydrolase. The second construct combined the P. canescens phytase gene and the bgaS promoter region encoding homologous beta-galactosidase. Both expression cassettes were transformed into P. canescens host strain containing xlnR. Phytase synthesis was observed only for strains with the bgaS promoter on arabinose-containing culture media. In conclusion, the bgaS and axhA promoters were regulated by different inducers and activators in the P. canescens strain containing a structural tandem of the axhA promoter and the gene of the xlnR xylanolytic activator.

Isolation and characterization of extracellular alpha-galactosidases from Penicillium canescens

Two alpha-galactosidases were purified to homogeneity from the enzymatic complex of the mycelial fungus Penicillium canescens using chromatography on different sorbents. Substrate specificity, pH- and temperature optima of activity, stability under different pH and temperature conditions, and the influence of effectors on the catalytic properties of both enzymes were investigated. Genes aglA and aglC encoding alpha-galactosidases from P. canescens were isolated, and amino acid sequences of the proteins were predicted. In vitro feed testing (with soybean meal and soybean byproducts enriched with galactooligosaccharides as substrates) demonstrated that both alpha-galactosidases from P. canescens could be successfully used as feed additives. alpha-Galactosidase A belonging to the 27th glycosyl hydrolase family hydrolyzed galactopolysaccharides (galactomannans) and alpha-galactosidase C belonging to the 36th glycosyl hydrolase family hydrolyzed galactooligosaccharides (stachyose, raffinose, etc.) of soybean with good efficiency, thus improving the digestibility of fodder.

Isolation and characterization of extracellular pectin lyase from Penicillium canescens

Pectin lyase A (molecular weight 38 kD by SDS-PAGE, pI 6.7) was purified to homogeneity from culture broth of the mycelial fungus Penicillium canescens using chromatographic techniques. During genomic library screening, the gene encoding pectin lyase A from P. canescens (pelA) was isolated and sequenced, and the amino acid sequence was generated by applying the multiple alignment procedure (360 residues). A theoretical model for the three dimensional structure of the protein molecule was also proposed. Different properties of pectin lyase A were investigated: substrate specificity, pH- and temperature optimum of activity, stability under different pH and temperature conditions, and the effect of Ca2+ on enzyme activity. In the course of the laboratory trials, it was demonstrated that pectin lyase A from P. canescens could be successfully applied to production and clarification of juice.

Use of a dual-origin temperature-controlled amplifiable replicon for optimization of human interleukin-1 beta synthesis in Escherichia coli

A new dual-replicon recombinant plasmid, pPR53-tsr, has been constructed; it is a derivative of the expression vector pPR-TGATG-1 [Mashko et al., Gene 88 (1990) 121-126]. In contrast to its progenitor, pPR53-tsr is a low-copy-number (low-Cop) plasmid amplifiable in temperature-dependent fashion. In addition to both the replicon and the par locus from plasmid pSC101, providing segregational stability and a low Cop at 28 degrees C, the new plasmid contains a mutant ColE1 replicon whose RNAII is synthesized under the control of the pL promoter. The presence of a thermolabile repressor, cIts857, allows the thermo-inducible amplification of pPR53-tsr; the increased plasmid Cop is estimated at approx. 200 per genome 6 h after thermal induction at 42 degrees C. Thus, pPR53-tsr can be used as a donor of the thermo-inducible dual-replicon fragment for recombinant plasmids. Here, we employ such an approach for optimization of production of human interleukin-1 beta (hIL-1 beta) in Escherichia coli at a high level. The thermo-induced level of recombinant hIL-1 beta (re-hIL-1 beta) biosynthesis was around 9% of total cellular protein when the dual-replicon high-Cop vector was used. A method based on acidification of the water-soluble protein fraction to pH 4.0 has been developed that allows for the isolation of 80%-pure re-hIL-1 beta. The homogeneous material was obtained by two subsequent hydrophobic sorbent chromatographies. The protein yield ranged between 3-5 mg of re-hIL-1 beta/g of wet cells. The re-hIL-1 beta specific activity was about 2 x 10(8) units/mg, coinciding with that of the authentic hIL-1 beta.