Bio-preservative Activities of Partially Purified Bacteriocin Extracts of Lactobacillus mindensis TMW and Lactobacillus tucceti CECT 5920 Isolated from Nigerian Fermented Foods

The preservative potentials of lactic acid bacteria (LAB) recovered from some Nigerian traditional fermented foods were assessed by inoculating 0.1 ml aliquots of suitable dilutions of the food samples on De Man Rogosa Sharpe (MRS) agar fortified with 50mg of nystatin. The isolates were assessed for their ability to produce bacteriocin using Agar Well Diffusion assay method. By using (GTG)5-PCR and 16s rDNA sequencing tools, two bacteriocin-producing LAB namely Lactobacillus tucceti CECT 5920 and Lactobacillus mindensis TMW were identified. Both LAB isolates had equal level of bacteriocin activity. Studies on inhibitory activity of partially purified bacteriocin extracts showed that temperature of 35°C had maximum effect on bacteriocin antimicrobial activity of L. tucceti CECT 5920 against Staphylococcus aureus NCTC 8325 and Escherichia coli 0157:H7, while pH had same effects on both LAB isolates against the test bacteria. Maximum tolerance of acidic medium was exhibited by both LAB isolates at pH 3-8. Bacteriocin inhibitory activity was best against both test bacteria at 0.2% concentration of NaCl. Combination of ginger with partially purified bacteriocin sample from both LAB isolates had reduction effect on both test pathogens for both Lactic acid bacteria isolates. When stored for 14 days, bacteriocin activity was optimum for the first day against both test pathogens, but decreased progressively with increased in storage time. The two LAB isolates had similar inhibitory activity against both test pathogens. L. tucceti CECT 5920 gave greater reduction result (90.03%) on S. aureus NCTC 8325 in fish sample and 78.07% against E. coli 0157:H7 in meat sample while L mindensis TMW had highest significant reduction effect (90.12%) in fish sample against S. aureus NCTC 8325 and 77.80% against E. coli 0157:H7 in fish sample. Both LAB isolates will perform well as preservative agents in food preservation as they showed production of bacteriocin which has antimicrobial activity and rapid acidification in growth medium.

Biodegradation of Palm Oil Mill Effluent.

Aims: The aim of this study was to investigate the biodegradation capacity of selected indigenous fungal isolates and optimization of their degradation ability using various environmental factors such as pH, incubation temperature, nutrient concentration and inoculums size in reducing pollution effect of palm oil mill effluent (POME) in the environment. Place and Duration of Study: Two fungal isolates Candida rugosa and Geotrichum candidum used in this work were previously isolated from POME sample collected from Starline palm oil mill industries, Umukalika, Obingwa LGA, Abia state Nigeria in previous work of authors. The study was carried out from March to August, 2013. Methodology: Spore suspension was prepared by adding 10 ml of 0.1% Tween 80 onto PDA slant of 5 days old culture of Candida rugosa and Geotrichum candidum respectively. Biodegradation of POME was carried out by inoculating 0.1ml (106spores/ml) of respective fungal isolates into different 500 ml Erlenmeyer flasks containing 100ml each of raw POME. They were incubated at 30ºC on a rotary shaker (200rpm). Samples were taken every 24hrs for 144hrs to determine BOD, COD, oil & grease. Similarly, optimization of biodegradation was carried out by studying the effect of different environmental conditions such as different initial pH levels (4.0-8.0), incubation temperature (25-50ºC), concentrations of soy bean (1.5-4.5% w/v) and inoculum size (0.1-0.5 v/v). The experiments were done in triplicates. Results: Biodegradation studies with selected indigenous fungi showed that C. rugosa was able to remove (44.6%) BOD, (13.9%) COD , (50.7%) oil and grease (O&G) while G. candidum reduced BOD, COD, O&G by 46.9%,16.9% and 64,9% respectively after 144hrs. Optimization of degradation in POME using various environmental and nutrients conditions revealed that at pH 8, C. rugosa showed best degradation of COD (48.6%), BOD (74.5%), O&G (41.8%) removal while COD (59.1%), BOD (75.7%) , O&G (59.1%) removal was observed with G. candidum treatment. The optimal incubation temperature for degradation using each of fugal isolates was at 35ºC with 85.2% BOD , 71.8% COD and 67.3% O&G removal for C. rugosa , 87.3% BOD and 63.4% COD for G. candidum .The best degradation ability for C. rugosa and G. candidum were demonstrated at 3.5w/v and 2.5w/v soybean concentrations respectively. The result also showed that increase in inoculum size could not completely reduce oil and grease during degradation process possibly because no single culture supports degradation optimally due to presence of complex sugars Conclusion: The selected fungal isolates exhibited high efficiency for removal of oil and grease as well as organic matter from POME but required control of environmental conditions and nutrient expansion for the effective biodegradation of POME.

Lipase Production by Fungal Isolates Grown in Palm Oil Mill Effluent.

Aims: The present work is aimed at determining the optimum conditions of pH, temperature and nitrogen concentration for lipase production by Candida rugosa and Geotrichum candidum in POME. Place and Duration of Study: This work was carried out at the Department of Microbiology, Michael Okpara University, Umudike-Abia state, Nigeria from July to December, 2013. The organisms used in the study were isolated in a previous work by the authors. Methodology: Five milliliter of sterile water was added to respective agar slant containing the two different fungal isolates while developed growth was scrapped with sterile needle and subsequently transferred into nutrient broth contained in 250 mL Erlenmeyer flasks. These flasks were further incubated for 48 h at 28ºC on rotary shaker at 180rmp. At this stage 0.1 mL of inoculum was transferred to the production medium (POME) and incubated for 144 h. Results: At initial pH6.0, C. rugosa produce maximum lipase activity of 26.37 UmL-1 while G. candidum showed highest activity of 29.4 UmL-1 at pH 7. C. rugosa alo showed maximum lipase activity of 27.8 UmL-1 at 30ºC while G. candidum produced highest lipase activity (24.9 UmL-1) at 35ºC. The use of soybean meal in the optimization of production lipase revealed that at concentration of 3.5%w/v, the respective fungi isolates were best supported for lipase yield with maximum activity of 25.97 UmL-1 by C. rugosa and 28.32 UmL-1 by G. candidum. Conclusion: This work evaluated the effect of three culture conditions (pH, temperature and nitrogen conc.) on lipase production by G. candidum and C. rugosa cultivated in POME. Results reveal that the factors were critical to growth and lipase production by the organisms and may be useful indices in the production of lipase even from other oil processing effluents.