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Lipopeptides are diverse metabolites produced by various bacterial and fungal genera. They are known for their antimicrobial and surfactant activities with diverse environmental, pharmaceutical, and also agronomic applications as biocontrol agents. In this study, a PCR was used to confirm the presence of NRPS genes in Bacillus mojavensis I4. This bacterial strain could produce diverse lipopeptides which belong to the fengycin, and surfactin families. The antioxidant activity of I4 biosurfactants was determined through four different in vitro assays. Furthermore, antimicrobial activity assays indicated that I4 lipopeptides exhibited marked inhibitory activity against several bacterial and fungal strains. Further treatment of potato dry rot causative pathogen Fusarium solani with I4 lipopeptides demonstrated a remarkable reduction in the fungal penetration by almost 80% after 15 days of incubation. The findings suggest that I4 lipopeptide is a potential biocontrol agent during potato tuber storage., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Response surface methodology was applied to optimize the production of biosurfactants from Bacillus mojavensis I4 using Box-Behnken design with four variables. The optimal variable combination was 3% of glucose as carbon source, 0.6% of glutamic acid as nitrogen source, temperature of 35 °C and 10 g/l of NaCl which yielded to an optimal production of 4.12 g/l. Compositional analysis and FTIR spectrum revealed that the extracted biosurfactants was a lipopeptides. The biosurfactants achieved a critical micelle concentration value of 100 mg/l. Moreover, the extracted biosurfactants were effective at recovering up to 89.2% of motor oil from sand beach and achieved a dispersion rate of 78% of the initial diameter of the oil. These findings suggested the potential use of I4 biosurfactants in the oil industry.

Medium composition and culture conditions for the xylanases production by Bacillus mojavensis A21 were optimized using two statistical methods: Plackett-Burman design applied to find the key ingredients and conditions for the best yield of enzyme production and Box-Behnken design used to optimize the value of the four significant variables: barley bran, NaCl, agitation, and cultivation time. The optimal conditions for higher production of xylanases were barley bran 18.66 g/l, NaCl 1.04 g/l, speed of agitation 176 rpm and cultivation time 34.08 h. Under these conditions, the xylanase experimental yield (7.45 U/ml) closely matched the yield predicted by the statistical model (7.23 U/ml) with R² = 0.98. The medium optimization resulted in a 6.83-fold increase in xylanase production compared to that of the initial medium. Best xylanase activity was observed at the temperature of 50 °C and at pH 8.0. The enzyme retained more 96% of its activity after 24 h at pH ranges from 7.0 to 90.0. The enzyme preserved more 80% of its initial activity after 60 min of pre-incubation from 30 °C to 60 °C. The main hydrolysis products yielded from corncob extracted xylan were xylobiose and xylotriose, suggesting the good potential of strain A21 in xylooligosaccharides production., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Lichenase from Bacillus licheniformis UEB CF was immobilized on Amberlite IR120 H. The immobilization yield and lichenase activity were 87 and 92.81 % of initial activity, respectively. The immobilized enzyme exhibited a shift in the optimal pH from 5.0 to 3.0, but the activity optimal temperature was not affected. The immobilized enzyme showed a residual activity of 50 % after five uses. It also exhibited high storage stability and retained 50 % of its initial activity after 120 days at 4 °C. The main hydrolysis products yielded from lichenan were trisaccharide and tetrasaccharide. The resulting mixed-linkage beta-oligosaccharides could be used as a special nutriment for lactic bacteria.

We have described previously the potential use of an alkaline protease from Bacillus pumilus CBS as an effective additive in laundry detergent formulations [B. Jaouadi, S. Ellouz-Chaabouni, M. Ben Ali, E. Ben Messaoud, B. Naili, A. Dhouib, S. Bejar, A novel alkaline protease from Bacillus pumilus CBS having a high compatibility with laundry detergent and a high feather-degrading activity, Process Biochem, submitted for publication]. Here, we purified this enzyme (named SAPB) and we cloned, sequenced and over-expressed the corresponding gene. The enzyme was purified to homogeneity using salt precipitation and gel filtration HPLC. The pure protease was found to be monomeric protein with a molecular mass of 34598.19Da as determined by MALDI-TOF mass spectrometry. The NH2-terminal sequence of first 21 amino acids (aa) of the purified SAPB was AQTVPYGIPQIKAPAVHAQGY and was completely identical to proteases from other Bacillus pumilus species. This protease is strongly inhibited by PMSF and DFP, showing that it belongs to the serine proteases superfamily. Interestingly, the optimum pH is 10.6 while the optimum temperature was determined to be 65 degrees C. The enzyme was completely stable within a wide range of pH (7.0-10.6) and temperature (30-55 degrees C). One of the distinguishing properties is its catalytic efficiency (kcat/Km) calculated to be 45,265min(-1)mM(-1) and 147,000min(-1)mM(-1) using casein and AAPF as substrates, respectively, which is higher than that of Subtilisin Carlsberg, Subtilisin BPN' and Subtilisin 309 determined under the same conditions. In addition, SAPB showed remarkable stability, for 24h at 40 degrees C, in the presence of 5% Tween-80, 1% SDS, 15% urea and 10% H2O2, which comprise the common bleach-based detergent formulation. The sapB gene encoding SAPB was cloned, sequenced and over-expressed in Escherichia coli. The purified recombinant enzyme (rSAPB) has the same physicochemical and kinetic properties as the native one. SapB gene had an ORF of 1149bp encoding a protein of 383 aa organized into a signal peptide (29 aa), a pro-protein (79 aa) and a mature enzyme (275 aa). The deduced amino acid sequence inspection displays an important homology with other bacterial proteases. The highest homology of 98.1% was found with BPP-A protease from Bacillus pumilus MS-1, with only 8 aa of difference.