Response Surface Methodology-Based Optimization of the Chitinolytic Activity of Strain 614 Exerting Biological Control against Phytopathogenic Fungi.

As part of the development of alternative and environmentally friendly control against phytopathogenic fungi, could be a useful species notably via the generation of hydrolytic enzymes like chitinases, which can act as a biological control agent. Here, a S614 strain exhibiting chitinase activity was isolated from a soil in southern Tunisia. Then, response surface methodology (RSM) with a central composite design (CCD) was used to assess the impact of five factors (colloidal chitin, magnesium sulfate, dipotassium phosphate, yeast extract, and ammonium sulfate) on chitinase activity.

Isolation of a chitinolytic Bacillus licheniformis S213 strain exerting a biological control against Phoma medicaginis infection.

Among nine chitinase-producing strains isolated from Tunisian soil, one isolate called S213 exhibited a potent chitinolytic activity. S213 strain was identified as Bacillus licheniformis by API 50CH system and sequence analysis of its partial 16S ribosomal DNA. Chitinolytic activity was induced either by colloidal chitin or fungal cell walls, and the highest chitinase activity reached at the late stationary phase exhibiting optimal temperature and pH of 50-60 °C and pH 6.

Putative use of a Bacillus subtilis L194 strain for biocontrol of Phoma medicaginis in Medicago truncatula seedlings.

An antagonist L194 strain against Phoma medicaginis pathogenic fungi was isolated from Tunisian soil (vicinity of Tunis) and identified as Bacillus subtilis based on biochemical characteristics and partial 16S rDNA sequence. When cells were grown in a minimal medium for 24 h, spore culture supernatant exhibited 2-fold higher antifungal activity than vegetative cells. MALDI-TOF mass spectrometry analysis showed that L194 spores produced mainly iturins, surfactins and fengycins with long-chain fatty acids, and other not yet identified compounds.

Structural investigation and homology modeling studies of native and truncated forms of alpha-amylases from Sclerotinia sclerotiorum.

The filamentous ascomycete Sclerotinia sclerotiorum is well known for its ability to produce a large variety of hydrolytic enzymes for the degradation of plant polysaccharide material. Two alpha-amylases designated as ScAmy54 and ScAmy43 were biochemically characterized and predicted to play an important role in starch degradation. Those enzymes produce specific oligosaccharides, essentially maltotriose, that have a considerable commercial interest.

Optimization of medium composition for the production of antimicrobial activity by Bacillus subtilis B38.

An antimicrobial activity produced by Bacillus subtilis B38 was found to be effective against several bacteria, including pathogenic and spoilage microorganisms such as, Listeria monocytogenes, Salmonella enteridis, and clinical isolates of methicillin-resistant Staphylococcus species. Nutrients such as carbon, nitrogen sources, and inorganic salts enhanced the production level of the antibacterial activity by B. subtilis B38.

Purification, characterization, and partial primary sequence of a major-maltotriose-producing alpha-amylase, ScAmy43, from Sclerotinia sclerotiorum.

A novel alpha-amylase (alpha-1,4-alpha-D-glucan glucanohydrolase, E.C. 3.

Production of anti-methicillin-resistant Staphylococcus activity from Bacillus subtilis sp. strain B38 newly isolated from soil.

B38 bacterial strain, isolated from Tunisian soil showed a strong antimicrobial activity. Based on biochemical characterization and 16S rDNA sequence analysis, B38 strain was identified as Bacillus subtilis. Cell culture supernatant showed antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus species and several Gram-positive and Gram-negative bacteria.