Aims: Laccases are diphenol oxidases that have numerous applications in biotechnological processes. In this work, the production of fungal laccase using organic and inorganic feed substrates in submerged static fermentation was investigated. Study Design: One-factor-at-a-time strategy was adopted to optimize the cultural parameters for enhanced laccase production. Place and Duration of Study: Department of Microbiology, Faculty of Science, University of Port Harcourt, Nigeria, between October 2014 and November 2015. Methodology: A total of nine fungal isolates were obtained from wood decaying sites of University of Port Harcourt forest areas and subjected to laccase screening with 2,2-Azinobis-3-ethyl(benzthiazoline-6-sulphonate) (ABTS). The influence of medium components using the basal medium at pH 5.0 as base was evaluated and these cultural parameters include carbon sources (glycerol, rice bran, glucose and ground orange peelings), nitrogen sources (yeast extract, potassium nitrate, peptone and ammonium chloride), metal ions (copper sulfate and manganese sulfate) and inducer compounds (ABTS, Tween 80 and soya oil). Time course study was conducted with the unoptimized and optimized cultural medium. Results: Out of nine cultures tested, seven were found to be laccase-positive with isolates CF-1 and CF-2 being the best potential cultures. Isolate CF-1 which had the highest laccase activity was identified as Pleurotus ostreatus and was chosen for further studies. Ground orange peelings (0.1% w/v) and NH₄Cl (0.1% w/v) were the most suitable carbon and nitrogen source for laccase production by the fungus. Maximum laccase production was obtained with Cu²⁺ at a concentration of 0.05%w/v among other metal ions. Soya oil at concentration of 0.05% (v/v) was the best inducer of the enzyme. The highest laccase production was achieved at an Initial pH 4.5. Under optimal culture medium, the maximum laccase activity was determined to be 7.21 U ml^-1 on the 7th day of cultivation; which was approximately three times higher than that in basal medium (2.5 U ml^-1). The results obtained indicate that the extracellular laccase production is dependent on various cultural parameters. Conclusion: One-factor-at-a-time strategy adopted in this study proved that the optimum conditions enhanced laccase production by three folds using orange peelings. The results obtained are very interesting since orange peelings are common agricultural wastes in several countries and imply that their re-utilization in the production of enzymes would help solve pollution problems caused by their improper disposal. In addition, Pleurotus ostreatus having shown promise for laccase production using low-cost lignocellulosic substrates could be suggested as a prospective candidate for higher laccase production for several biotechnological applications.

Aim: To optimize media components and cultural conditions using response surface methodology (RSM) in the production of invertase by Aspergillus niger grown on potato peels (P1) and pineapple peels (P2). Place and Duration of Study: The study was conducted at Environmental Microbiology laboratory, University of Port Harcourt, Choba between September 2015 and January 2017. Methodology: Chemical analyses of P1 and P2 were carried out using standard methods. Invertase production was screened using Fehling solution test coupled with invertase activity assay. Reducing sugar was estimated using dinitrosalicylic acid (DNS) procedure. The RSM optimization design involved four (4) independent variables (pH, temperature, pineapple peels concentrations, and potatoes peels concentrations) at five (5) levels, screened through thirty (30) different experimental runs using central composite design (CCD). Results: Optimal fermentation conditions that yielded maximum invertase (321.4 U/mL) and biomass (11.34 mg/mL) by A. niger was achieved with the combination of pH 9.0, temperature 35°C, pineapple peels concentration 10%, and potato peels concentration 50%. The model used gave a predicted R-Squared of -0.2258. Negative "Predicted R-squared” implies that the overall mean may be a better predictor of the response than the current model. "Adequate precision" of 6.190 was obtained, showing that the model can be used to navigate the design space. Conclusion: This result has demonstrated the efficiency of RSM technique to optimize invertase production from A. niger using potato and pineapple peels as substrates. The use of local substrates can make invertase production economically attractive.

Aim: This study reports the production and optimization of cellulase from Penicillium sp. using corn-cob (CC) and pawpaw fibre (PF) as substrates. Methods: Nine fungal isolates, obtained from compost soil, were screened for cellulolytic activity. Isolate CPF-1, based on its ability to give the highest zones of clearance and cellulolytic activity, was selected. CPF-1 was identified as Penicillium sp. based on its cultural and morphological characteristics. Cellulase activity was determined by the DNS method on Congo red agar plate. Effects of temperature, pH and metal ions (Zn²⁺, Hg²⁺, Fe²⁺, Mg²⁺, Ca²⁺ and Co²⁺) on crude cellulase activity and stability were studied using two substrates (corn-cob and pawpaw fibre) by solid state fermentation. Results: Data obtained from the study revealed that the optimal pH and temperature values for the production of crude cellulase by the Penicillium sp. were pH 5 and 30°C, respectively; with maximum cellulase activity of 37.32 IU/mL. Optimum cellulase productivity of 15.787 IU/mL was obtained with CC as the substrate while 2.141 IU/mL was obtained with PF substrate after 1 h of fermentation. The cellulase produced was most stable at pH 5 and temperature of 40°C. Fe²⁺ and Co²⁺ were able to stimulate cellulase activity whereas the other ions inhibited the enzyme activity. Conclusion: This study has revealed the potentials of corn-cob and pawpaw fibre as substrates for cellulase production by Penicillium sp. through solid state fermentation (SSF); with corn-cob as the most suitable substrate. Considering that these substrates are readily available, they present cheaper substrate alternatives for potential large-scale cellulase production.

Bacteriocin is a natal antimicrobial which can be exploited to evade the inevitability of adding chemical preservatives to food products. This study is aimed at the production and characterization of bacteriocin from Lactic acid bacteria (LAB) isolated from fermented food products. Sixteen (16) samples of various fermented food products (abacha, fufu, ogi and yoghurt) were screened for the presence of bacteriocin producing LAB using agar well diffusion method. The strain designated C6 was selected for further studies due to its broad inhibitory effect on the growth of all tested organisms (Enterococcus faecalis ATCC 33090, Pseudomonas aeruginosa MN 515053, Listeria innocua ATCC 2127, Staphylococcus aureus, Escherichia coli, Candida spp and Aspergillus terrus MN907795). Molecular characterization spotted C6 isolated from yoghurt as Lactobacillus fermentum (accession no. MN907811). Purification of the antimicrobial substance was achieved using High performance liquid chromatography (HPLC) with nisin as Standard which revealed it to be bacteriocin a proteinaceous antimicrobial that is stable to heat and organic solvents. Effect of substrate level on the growth of Lactobacillus fermentum and optimization of physicochemical parameters on bacteriocin production revealed optimum condition of 1.0 % glucose, 0.5 % sodium nitrate, pH of 6.0, incubation temperature of 35°C for 72h. This makes Lactobacillus fermentum and its bacteriocin a good antagonistic agent for exploitation in pharmaceutical and food processing industries as well as in the field of biotechnology.

‘Ncha iwu’ is commonly used as a sauce in the preparation of ready-to-eat African salad, a wellknowndelicacy among the Igbo tribe in Nigeria. A total number of fifteen (15) samples of ‘ncha iwu’ were randomly purchased from three (3) vendors in Orie Ngodo and Eke Eziama market in Umunneochi Local Government Area of Abia state. The microbiological quality, proximate composition, and mineral content of the samples were determined using Standard Methods. ‘Ncha iwu’ prepared in the laboratory served as the control. The results showed that total bacterial, Staphylococcal, Coliform and fungal counts of the samples ranged from 3.81-4.37, 2.0-3.58, 3.0-3.8, and 2.0-3.0 log10 CFU/g, respectively. The bacterial species isolated and frequency of occurrence were Staphylococcus aureus (28 %), Klebsiella spp. (18 %), Pseudomonas spp. (18 %), Escherichia coli (18 %) while the fungal species were Penicillium spp. (50 %), Aspergillus spp. (40 %), and Candida spp. (10 %). Proximate analysis indicated that ‘ncha iwu’ contains ash (63.93%), moisture (15.88 %), fibre (8.99 %), lipid (7.70 %), protein (3.50 %) and carbohydrate (0.0 %) while minerals content include Fe (3.679 mg/g), Mg (1.055 mg/g), K (1.054 mg/g), Ca (1.030 mg/g), Mn (0.469 mg/g) and Na (0.222 mg/g). Although ‘ncha iwu’ contains beneficial nutrients, majority of the commercial samples were contaminated with potential pathogenic microorganisms which is a public health concern unlike the control. This is as a result of poor handling by the producers and vendors. Good hygienic practices by the handlers, proper packaging and storage of ‘ncha iwu’ will reduce the microbial contamination of the product. Hence, adequate public health awareness campaign, training on food safety, sanitation and hygenic practices should be provided to the local processors and vendors of ‘ncha iwu’.