Prof.  Nawel  Boucherba
University of Bejaia,  Algeria

Title: A twenty year retrospective of work on microbial enzymes isolated from Algerian sites

Abstract:

Our work began on enzymes in 2004 on the topic : xylanases and after ten years, we are interested in several types of enzymes of industrial interest such as amylase, keratinase, peroxydase, cellulase and lipase, much of the work was carried out in collaboration with differents laboratories in Algeria, Spain, Finland, France, Tunisia and South Africa. The first isolated and purified enzyme was xylanase produced by Jonesia denitrificans BN-13, the enzyme was a thermotolerant biocatalyst working at 50 °C and at pH 7.0. The xylanase was considered as a thermotolerant biocatalyst interesting for biotechnological applications. It was the first report in the scientific literrature on the production of such enzyme by Jonesia denitrificans BN13 which grows well on a medium containig agricultural byproducts like orange peel, esparto grass, retam and alfa, we have tested a low-cost extraction system using aqueous phase, in this system ; the enzyme activity was located in the lower phase with a partition coefficient of 0.67 and a purification factor of 1.78. We also isolated two xylanases from Bacillus safensis CBLMA18 : Xyn11A is an extracellular 22.5-kDa GH11 xylanase while a second xylanase, Xyn10B, corresponds to an intracellular 48-kDa GH10 enzyme. Both unimodular xylanases showed activity only on xylan substrates with important differences in their catalytic pattern. Xyn11A displays higher activity on beechwood xylan, meanwhile Xyn10B prefers arabinoxylans. We explore also the limits of hyperthemophilic Pyrococcus horikoschii endoglucanase (PhEG) to tolerate superbase ionic liquids (SIL). The Results reveal new ways to design a beneficial combination of SIL. In another study, telluric samples collected from different regions of Algeria were processed for the isolation of novel peroxidase-producing actinobacterial strains. The 16S rRNA gene sequencing showed that most of the strains belong to the genus Streptomyces. The canola lignocellulosic waste induced peroxidase in the Strain Streptomyces rochei S19 which was selected for further optimization and the purified extracellular peroxidase showed a single band estimated molecular weight of 21.45 kDa, the presence of genes encoding for peroxidase and for carbohydrate-active enzymes were detected. The isolation of actinobacteria able to produce extracellular lipases were investigated using olive mill wastewater (OMW), maximum lipase activity was detected for a strain identified as a Streptomyces sp. Strain 22 dz. To enhance lipase production, RSM has been adopted, the optimization results obtained showed that the optimal lipase activity was achieved after a 9 days incubation time at pH 4, with an inoculum size of 1.7×10⁷ (spores/mL), incubated at a temperature of 30°C using 6% (v/v) OMW as the sole carbon source, the purification of the lipase was done using a conventional method. The purified lipase exhibited a molecular weight of 22 kDa. The maximal activity was obtained at a temperature of 30 to 40 °C. Keratinase was also isolated and purified from Streptomyces sp. Strain 06 dz, the optimum keratinase activity was obtained using 6.13 g/mL chicken feather meal as the sole carbon and nitrogen source, at pH 6.25, incubated at a temperature of 40.65 °C after an incubation period of 4.11 days and an inoculum size of 3.98×107 spores/mL.

Keywords : Bacteria, Actinomycete, enzyme, purification, characterization, byproducts, valorization.

Biography:

Nawel Boucherba has expertise in microbial enzymes especially : purification and characterization of amylases, lipases, keratinases, proteases, xylanases and peroxidases. Nawel Boucherba obtained her degree of Bachelor in Natural and Life Sciences in 1994 at Bouanani high School (Bejaia). She received a prize of excellence and won recognition of the best high school student in 1992. She obtained four degrees from Bejaia’s university: Applied university studies in quality control and food analysis, Engineer in food sciences, Magister in microbiology, University habilitation in 2014 and promoted to the degree of professor in 2020. She has published more than 70 peer-reviewed papers in international journals and has over than 150 contributions in national and international conferences held in 3 continents: Africa, Asia and Europe and she served as reviewer for many journals. Nawel Boucherba metrics: more than 600 citations in scientific publications and Hirsch index of 15.