Application of a statistical design to the optimization of parameters and culture medium for alpha-amylase production by Aspergillus oryzae CBS 819.72 grown on gruel (wheat grinding by-product).

The production optimization of alpha-amylase (E.C.3.2.1.1) from Aspergillus oryzae CBS 819.72 fungus, using a by-product of wheat grinding (gruel) as sole carbon source, was performed with statistical methodology based on three experimental designs. The optimisation of temperature, agitation and inoculum size was attempted using a Box-Behnken design under the response surface methodology. The screening of nineteen nutrients for their influence on alpha-amylase production was achieved using a Plackett-Burman design. KH(2)PO(4), urea, glycerol, (NH(4))(2)SO(4), CoCl(2), casein hydrolysate, soybean meal hydrolysate, MgSO(4) were selected based on their positive influence on enzyme formation. The optimized nutrients concentration was obtained using a Taguchi experimental design and the analysis of the data predicts a theoretical increase in the alpha-amylase expression of 73.2% (from 40.1 to 151.1 U/ml). These conditions were validated experimentally and revealed an enhanced alpha-amylase yield of 72.7%.

Optimization of submerged Aspergillus oryzae S2 α-amylase production.

Use of 4 agro-industrial by products and organic materials as nitrogen sources for production of Aspergillus oryzae S2 α-amylase in liquid culture was investigated. The 2 agro-industrial byproducts maltose and saccharose, and also lactose and starch were individually evaluated for use as carbon sources. A Box-Behnken experimental design was used to determine optimal conditions for production of α-amylase. A maximum amylase activity of 750 U/mL was obtained at a temperature of 24°C, a urea concentration of 1 g/L, and a C/N ratio of 2. Laboratory scale application of optimal conditions in a 7 L fermentor produced a final α-amylase activity of 770 U/mL after 3 days of batch cultivation. Addition of 10% starch to the culture medium each 12 h immediately after the stationary phase of cell growth led to a production yield of 1,220 U/mL at the end of fed-batch cultivation.

Biochemical and molecular characterization of Pseudomonas aeruginosa CTM50182 organic solvent-stable elastase.

An extracellular alkaline elastase was produced from Pseudomonas aeruginosa CTM50182. It was chromatographically purified using HPLC and Mono Q Sepharose column. Matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) analysis revealed that the purified enzyme (called AMPP) was a monomer with a molecular mass of 33,015.18 Da. The N-terminal 29 amino acid sequence of AMPP showed high homology with those of Pseudomonas elastases. It showed optimal activity at pH 12 and 80 °C and was stable at a pH range of 9-12 after 120 h of incubation. Its thermoactivity and thermostability were upgraded in the presence of 5 mM Co(2+). Its half-life times at 70 and 80 °C were 16 and 10 h, respectively. It was completely inhibited by ethylene glycol-bis (ß-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), and 1,10-phenanthroline, suggesting that it belongs to the metalloprotease family. AMPP also exhibited high catalytic efficiency, organic solvent-tolerance, and hydrolysis. The lasB gene encoding AMPP was cloned, sequenced, and expressed in Escherichia coli. The biochemical properties of the extracellular purified recombinant enzyme (rAMPP) were similar to those of native AMPP. This organic solvent-stable protease could be considered a potential candidate for application as a biocatalyst in the synthesis of enzymatic peptides.

Efficient transformation procedure of a newly isolated Streptomyces sp. TN58 strain producing antibacterial activities.

A new aerobic Gram-positive bacterium designated TN58 producing antibacterial activities against Gram-positive and Gram-negative bacteria was isolated from Tunisian soil. The nucleotide sequence of the 16S rRNA gene (1516 bp) of the TN58 strain showed high similarity (96-98%) to the Streptomyces 16S rRNA genes, especially with that of Streptomyces lavendulae which produces the anti-tumor compound mitomycin C, and the cyclic peptide antibiotic, complestatin. Cultural characteristic studies, alignment data of the 16S rRNA gene, and analysis of the nucleotide sequence of a 2.2 kb genomic DNA fragment from TN58 strongly suggested that this strain could be an actinomycete and most probably belongs to the genus Streptomyces. Study of the influence of different nutritional compounds on antibiotic production showed that the highest antibacterial activities were obtained when glycerol at 1% (w/v) was used as sole carbon source in the presence of potassium. In analytical conditions, the application to supernatant culture of the TN58 strain of various extraction and purification steps led to the isolation of two pure active molecules having a retention time of 38.6 and 50.2 min, respectively. TN58 strain was untransformable with the Streptomyces cloning vector pIJ702 via classical polyethylene glycol (PEG) protoplast transformation and previously described Streptomyces electroporation procedures. Transformation was rendered possible by the electroporation technique only after utilization of a preculture medium without sucrose and a regeneration plate containing a low sucrose concentration.