Antimicrobial polymers:The potential replacement of existing antibiotics?

Antimicrobial resistance is now considered a major global challenge; compromising medical advancements and our ability to treat infectious disease. Increased antimicrobial resistance has resulted in increased morbidity and mortality due to infectious diseases worldwide. The lack of discovery of novel compounds from natural products or new classes of antimicrobials, encouraged us to recycle discontinued antimicrobials that were previously removed from routine use due to their toxicity, e.g., colistin. Since the discovery of new classes of compounds is extremely expensive and has very little success, one strategy to overcome this issue could be the application of synthetic compounds that possess antimicrobial activities. Polymers with innate antimicrobial properties or that have the ability to be conjugated with other antimicrobial compounds create the possibility for replacement of antimicrobials either for the direct application as medicine or implanted on medical devices to control infection. Here, we provide the latest update on research related to antimicrobial polymers in the context of ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) pathogens. We summarise polymer subgroups: compounds containing natural peptides, halogens, phosphor and sulfo derivatives and phenol and benzoic derivatives, organometalic polymers, metal nanoparticles incorporated into polymeric carriers, dendrimers and polymer-based guanidine. We intend to enhance understanding in the field and promote further work on the development of polymer based antimicrobial compounds

Valorization of chicken feather through dekeratinization by keratinolytic Bacillus species to amino acid

The poultry meat processing sector generates chicken feathers as by-products, and they are 90percent keratin in composition. Keratin is an insoluble and structural protein that shows recalcitrance to hydrolysis by classical proteolytic enzymes, including trypsin, pepsin, and papain. Keratinases are a group of proteolytic enzymes endowed with keratin degradation into peptides and amino acids. They are recently gaining traction for their multifaceted potential application in the green industrial space. Hence, keratinolytic bacteria previously isolated from dumpsite were identified using 16S rDNA sequencing. The optimal fermentation conditions were determined for enhanced extracellular keratinase production and chicken feather degradation. Also, the amino acid analysis of the chicken feather hydrolysates was carried out. The biochemical properties of the keratinases were also determined. Based on 16S rDNA sequencing and phylogenetic analysis, the isolates coded as SSN-02 and HSN-03 showed a high percentage of sequence homology with Bacillus spp.; hence, they were identified as Bacillus sp. NFH5 and Bacillus sp. FHNM, respectively. Bacillus sp. NFH5 showed optimal keratinase production of 1149.99 ± 80.99 U/mL after 96 h of incubation time, in optimized fermentation conditions that included pH (4.0), chicken feather (1.5percent, w/v), inoculum size (3percent, v/v) and temperature (30 oC). Similarly, Bacillus sp. FHNM demonstrated the maximum keratinase production of 480 ± 41.14 U/mL 144 h post cultivation, in optimized fermentation conditions with pH (7.0), chicken feather (2.0percent, w/v), inoculum size (3percent, v/v) and temperature (30 oC). For Bacillus sp. NFH5 chicken feather hydrolysate, the amino acids in relatively higher concentration (>1.0g/100g sample) include arginine (1.8), serine (1.16), aspartic acid (1.95), glutamic acid (2.47), proline (1.16) and glycine (1.45). Bacillus sp. FHNM feather hydrolysates, contained (g/100g of sample): arginine (1.9), serine (1.4), aspartic acid (2.5), glutamic acid (2.51), glycine (1.51), proline (1.13), leucine (1.030, histidine (1.25), and lysine (1.06) (g/100g of sample) in high concentration. The keratinases were optimally active at pH 8.0. Bacillus sp. FHNM showed an optimal temperature of 100 oC; while Bacillus sp. NFH5 keratinase displayed optimal activity at 90 oC. EDTA and 1,10-phenanthroline inhibited the keratinases, and the inhibition pattern indicated that they belong to metalloprotease. Keratinase from Bacillus sp. FHNM showed considerable residual activity in the presence of Co²⁺ (93percent), Fe³⁺ (99percent), and K⁺ (94percent). Bacillus sp. NFH5 keratinase retained 92percent, 92percent, 93percent of the original activity against Ba²⁺, Na⁺ and Fe³⁺ treatment. Bacillus sp. FHNM keratinase was remarkably stable after 60 min of detergents treatment with residual activity of 89percent, 96percent, 81percent, 73percent, 96percent, 88percent, 88percent and 98percent for Omo, Surf, Ariel, Sunlight, Prowash, Freshwave, Sky, and Evaklin, respectively. Maq impacted the enzyme stability negatively, with residual activity of 48percent after 60 min of incubation. Additionally, keratinase Bacillus sp. NFH5 retained 68percent, 78percent, 80percent, 84percent, 57percent, 80percent, 98percent, 106percent and 106percent of the original activity against Omo, Surf, Ariel, Sunlight, Maq, Prowash, Freshwave, Sky and Evaklin, respectively. Therefore, these results suggest that Bacillus spp. could be ideal candidates for sustainable production of active keratinases and valorization of the abundantly generated keratinous biomass. The stability displayed by keratinases from Bacillus sp. FHNM and Bacillus sp. NFH5 suggests their promising candidacy for detergent formulation.Thesis (MSc) -- Faculty of Science and Agriculture, 202

Valorization of chicken feather through dekeratinization by keratinolytic Bacillus species to amino acid

The poultry meat processing sector generates chicken feathers as by-products, and they are 90percent keratin in composition. Keratin is an insoluble and structural protein that shows recalcitrance to hydrolysis by classical proteolytic enzymes, including trypsin, pepsin, and papain. Keratinases are a group of proteolytic enzymes endowed with keratin degradation into peptides and amino acids. They are recently gaining traction for their multifaceted potential application in the green industrial space. Hence, keratinolytic bacteria previously isolated from dumpsite were identified using 16S rDNA sequencing. The optimal fermentation conditions were determined for enhanced extracellular keratinase production and chicken feather degradation. Also, the amino acid analysis of the chicken feather hydrolysates was carried out. The biochemical properties of the keratinases were also determined. Based on 16S rDNA sequencing and phylogenetic analysis, the isolates coded as SSN-02 and HSN-03 showed a high percentage of sequence homology with Bacillus spp.; hence, they were identified as Bacillus sp. NFH5 and Bacillus sp. FHNM, respectively. Bacillus sp. NFH5 showed optimal keratinase production of 1149.99 ± 80.99 U/mL after 96 h of incubation time, in optimized fermentation conditions that included pH (4.0), chicken feather (1.5percent, w/v), inoculum size (3percent, v/v) and temperature (30 oC). Similarly, Bacillus sp. FHNM demonstrated the maximum keratinase production of 480 ± 41.14 U/mL 144 h post cultivation, in optimized fermentation conditions with pH (7.0), chicken feather (2.0percent, w/v), inoculum size (3percent, v/v) and temperature (30 oC). For Bacillus sp. NFH5 chicken feather hydrolysate, the amino acids in relatively higher concentration (>1.0g/100g sample) include arginine (1.8), serine (1.16), aspartic acid (1.95), glutamic acid (2.47), proline (1.16) and glycine (1.45). Bacillus sp. FHNM feather hydrolysates, contained (g/100g of sample): arginine (1.9), serine (1.4), aspartic acid (2.5), glutamic acid (2.51), glycine (1.51), proline (1.13), leucine (1.030, histidine (1.25), and lysine (1.06) (g/100g of sample) in high concentration. The keratinases were optimally active at pH 8.0. Bacillus sp. FHNM showed an optimal temperature of 100 oC; while Bacillus sp. NFH5 keratinase displayed optimal activity at 90 oC. EDTA and 1,10-phenanthroline inhibited the keratinases, and the inhibition pattern indicated that they belong to metalloprotease. Keratinase from Bacillus sp. FHNM showed considerable residual activity in the presence of Co²⁺ (93percent), Fe³⁺ (99percent), and K⁺ (94percent). Bacillus sp. NFH5 keratinase retained 92percent, 92percent, 93percent of the original activity against Ba²⁺, Na⁺ and Fe³⁺ treatment. Bacillus sp. FHNM keratinase was remarkably stable after 60 min of detergents treatment with residual activity of 89percent, 96percent, 81percent, 73percent, 96percent, 88percent, 88percent and 98percent for Omo, Surf, Ariel, Sunlight, Prowash, Freshwave, Sky, and Evaklin, respectively. Maq impacted the enzyme stability negatively, with residual activity of 48percent after 60 min of incubation. Additionally, keratinase Bacillus sp. NFH5 retained 68percent, 78percent, 80percent, 84percent, 57percent, 80percent, 98percent, 106percent and 106percent of the original activity against Omo, Surf, Ariel, Sunlight, Maq, Prowash, Freshwave, Sky and Evaklin, respectively. Therefore, these results suggest that Bacillus spp. could be ideal candidates for sustainable production of active keratinases and valorization of the abundantly generated keratinous biomass. The stability displayed by keratinases from Bacillus sp. FHNM and Bacillus sp. NFH5 suggests their promising candidacy for detergent formulation.Thesis (MSc) -- Faculty of Science and Agriculture, 202