Tube Fermentation Research Articles

Microbiological Evaluation of Different Types of Branded and Non-branded Ready-to-Eat Snacks Sold in Elementary Schools of District Peshawar, Pakistan

The lack of hygiene in the preparation and packing of ready-to-eat foods is fast becoming a serious public health concern, especially for school children. The intervention of different pathogenic microorganisms in these foods poses the risk of foodborne disease outbreaks. The current study was designed to assess bacterial contamination in different types of ready-to-eat (branded and non-branded) snacks purchased from September 2021 to December 2021 in various elementary schools of Peshawar, Pakistan. A total of 20 samples were collected and analyzed using the pour plate method for total plate count (TPC). Moreover, the multiple fermentation tube method was used for total coliforms (TC) and fecal coliforms (FC). Escherichia coli isolates were identified using E. coli O157:H7 latex test reagent kit Pro Lab, Canada. The results revealed contamination by TPC (6.67%), TC (40%), FC (33.33%), and E. coli (20%) in the samples. These values were higher than the permissible limits set by Food and Agriculture Organization (FAO). Hence, it was concluded that there is a practice gap in food safety knowledge among ready-to-eat food vendors. The vendors are usually untrained and lack the knowledge of proper hygiene and food handling procedures. It is suggested here that the government should pay special attention towards improving public awareness regarding food safety and quality of ready-to-eat foods sold in Peshawar, Pakistan.

Perbandingan Metode Membran Filter dan Metode Tabung Ganda Terhadap Kandungan Escherichia coli pada Air Bersih

Escherichia coli bacteria are bacteria used as indicators of contamination. Bacteriological water testing can use a Membrane Filtration (MF) and a Multiple Tube-Fermentation (MTF). This study aims to compare the membrane filtration and Multiple Tube-Fermentation methods on the presence of Escherichia coli in clean water. The two methods are compared to determine the percentage difference in the results of the two tests. The research methodology uses a description of observation. 20 samples of water boreholes were used and tested for the presence of Escherichia coli. Calculation of bacterial groups uses SNI standard references regulated by the Minister of Health of the Republic of Indonesia. The results showed that the average number of Escherichia coli bacteria by the Multiple Tube-Fermentation method was less than the Membrane Filtration method. There is a difference in the percentage of the results of the two tests by 40%. Multiple Tube Fermentation is more sensitive than the Membrane Filtration method for detecting the presence of Escherichia coli in clean water.Keywords : Water, Escherichia coli, Membrane filtration, Multiple tube-fermentation

Antifungal Susceptibility Pattern of Candida Isolates: A Comparison in H.I.V. Positive and Negative Patients from A Tertiary Care Hospital of Northern India

Candidiasis is recognized as a significant cause of morbidity, especially in immunocompromised individuals. An epidemiologic change in Candida species and emergence of resistance can impact the usage of antifungal agents as empirical therapy for Candidiasis in patients with or without AIDS. The present study was done to find out: i) The species of Candida isolated from H.I.V. and Non-HIV infected patients. ii) The resistance pattern of these Candida isolates to antifungal agents. A total of 160 Candida species isolates (80 isolates each from H.I.V. and Non-HIV infected patients) were characterized. Identification of yeast isolates was made by standard procedures including morphology (Staib agar, cornmeal agar, CHROMagar), germ tube test, fermentation, and assimilation of sugars and growth at 42°C. In addition, sensitivity testing was done using the broth microdilution method (M27-A2) as per the C.L.S.I. guidelines against amphotericin B, nystatin, voriconazole, fluconazole, ketoconazole, and itraconazole. In both the groups, i.e., H.I.V. and Non-HIV infected patients, Candida albicans was the most common species (61.2 % and 85 % respectively), followed by Candida guilliermondi (16.2 % and 5 %), Candida tropicalis (5 % and 3.7 %), Candida krusei (5% and 2.5 %), Candida dubliniensis 1(5 % and 1.2 %) and others. Among HIV infected patients fluconazole resistance was 16.25%, ketoconazole 13.5%, clotrimazole 12.5%, itraconazole 6.25 %. In the non-HIV infected group, fluconazole resistance was 8.75% and itraconazole 1.25%. For the appropriate treatment of Candida infections, antifungal susceptibility has become an essential tool, especially in the present scenario of increasing resistance.

An in vitro batch fermentation protocol for studying the contribution of food to gut microbiota composition and functionality.

Knowledge of the effect of foods on gut microbiota composition and functionality is expanding. To isolate the effect of single foods and/or single nutrients (i.e., fiber, polyphenols), this protocol describes an in vitro batch fermentation procedure to be carried out after an in vitro gastrointestinal digestion. Therefore, this is an extension of the previous protocol described by Brodkorb et al. (2019) for studying in vitro digestion. The current protocol uses an oligotrophic fermentation medium with peptone and a high concentration of fecal inoculum from human fecal samples both to provide the microbiota and as the main source of nutrients for the bacteria. This protocol is recommended for screening work to be performed when many food samples are to be studied. It has been used successfully to study gut microbiota fermentation of different foodstuffs, giving insights into their functionality, community structure or ability to degrade particular substances, which can contribute to the development of personalized nutrition strategies. The procedure does not require a specific level of expertise. The protocol takes 4-6 h for preparation of fermentation tubes and 20 h for incubation.

β-glucan formation is a selective advantage for beer-spoiling Levilactobacillus brevis TMW 1.2112 during planktonic growth

Some lactic acid bacteria (LAB) isolated from beer or wine produce capsular β-glucans from UDP-glucose via the membrane-anchored glycosyltransferase GTF-2. This phenomenon is feared in breweries, because the viscosity of the affected liquids drastically increases due to the β-glucan and concomitant pellicle formation of these LAB. Currently it is unknown if this type of polysaccharide formation provides any advantage for the producing LAB during the colonization of (ethanol-containing) liquids. We thus used the β-glucan producer Levilactobacillus (L.) brevis TMW 1.2112 and its β-glucan-deficient transposon mutant (Δ gtf-2), and compared their growth at different ethanol concentrations and their competitiveness during co-cultivation. No significant inhibition in growth and differences in acidification were observed for both strains up to ethanol concentrations of 8% (v/v). At 10 % ethanol, the β-glucan forming wildtype increased its cell number and produced more acid in comparison to the mutant strain, which settled at the bottom of the fermentation tubes at any tested condition. At higher ethanol concentrations (12–18 % v/v) both strains failed to grow, while a higher viability of the wildtype strain was observed. After co-cultivation of both strains for up to 72 h in liquid nutrient medium (without ethanol), significantly more ropy wildtype colonies were detected, if the wildtype had been initially applied in similar cell counts or in excess. By contrast, the number of smooth mutant colonies was solely significantly higher after 24 h of growth, if the mutant strain had been initially inoculated in excess. These results indicate that the β-glucan-mediated pellicle formation by L. brevis TMW 1.2112 is its dominant phenotype and a selective advantage during colonization of liquids.

Microbiological and Biochemical Contamination Analysis of Refilled Drinking-water in Abeli, Kendari, Southeast Sulawesi

BACKGROUND: The access to safe drinkingwater is increasingly difficult, especially in water catchment or coastal areas. Due to the difficulty, people in coastal areas tend to consume ready-to-use refilled drinking-water. However, the sanitation facilities on most drinking-water refill depots do not meet the requirements, hence really prone to microbial contamination. We conducted this study to determine the types of bacteria causing the contamination of refilled drinking-water from refill depots in Abeli, a coastal area in Kendari.METHODS: Samples were collected from all 6 drinkingwater refill depots in Abeli. Three-series fermentation tubes were used for the microbiological test, including the presumptive, confirmative and completed tests. The biochemical test was performed with indole test, methyl red test, Voges-Proskauer test, and citrate utilization test (IMViC) methods and the triple sugar iron agar (TSIA) test.RESULTS: Among 6 refilled drinking-water samples, we found the growth of coliform bacterial colonies in 3 samples, exhibiting various characteristics. Based on the characteristics, both microbiological and biochemical, the identified bacteria were Proteus sp., Escherichia coli and Klebsiella oxytoca.CONCLUSION: Bacteria that contaminated refilled drinking-water in Abeli were Proteus sp., E. coli and K. oxytoca. Continuous supervision is required to ensure the quality of water from drinking-water refill depots.KEYWORDS: bacteria, Proteus sp., Escherichia coli, Klebsiella oxytoca, coastal areas, refilled drinking water

Bacteriological quality of water samples from Kochi, Southwest Coastal India and its implications

BACKGROUND: Coliforms and other bacterial indicators are known to be present in Community water samples causing faecal pollution of water. There is also a growing body of evidence demonstrating that the aquatic environmental microbes are drug resistant. OBJECTIVE: The objective of this study was to evaluate the microbial quality of the water from tap, well and pond in urban households of Kochi, Kerala state. MATERIALS AND METHODS: A total of 100 water samples (46 from well water, 45 from tap water and 9 from lakes and ponds) were analysed by the multiple fermentation tube method to determine the presumptive coliform count or the most probable number (MPN) of coliforms, and the isolates were identified using standard procedures, followed by susceptibility testing. RESULTS: Eighty samples were positive for growth (76 grew coliforms, four samples grew non-pathogens). A total of 105 coliform isolates were grown in culture. The MPN numbers were noted to be >100 for over 50% of all the samples (n = 56), thus making the water unsatisfactory for drinking purposes. The highest number of organism isolated was Klebsiella pneumonia (n = 55), followed by Enterobacter spp (n = 34) and Escherichia coli (n = 16). Well water had the highest proportion of all three of these organisms. Up to 26%–40% resistance was seen to amoxicillin–clavulanic acid and 5.4%–5.8% of resistance was noted to third-generation cephalosporins, while two isolates were extended-spectrum beta-lactamase-producing Enterobacteriaceae (CTX-M and TEM types). CONCLUSION: The city municipal water authorities need to adopt more aggressive treatment/disinfection practices to combat high coliform contamination. The bacteriological quality of well water at the source needs to be monitored. Meanwhile, continued adequate home purification is suggested for drinking water. The city water does not pose a threat of antibiotic resistance for now. Environmental sampling should be given equal priority as clinical sampling in the coming days.

Biocorrosion Inhibitory Potential of Aqueous Extract of Phyllanthus amarus against Acid Producing Bacteria

Biocorrosion is a form of corrosion of metallic and concrete materials mediated by microorganisms. Acid producing bacteria are major culprits in the corrosion of materials in the environment. This study focused on the inhibition of biocorrosion by acid producing bacteria using aqueous extract of Phyllanthus amarus (PAAE). Acid producing bacteria were isolated from produced water samples collected from oilfields located in Niger Delta, Nigeria. Multiple fermentation tube technique was adopted for the isolation of the acid producing bacteria using phenol red dextrose broth as culture broth medium. The gravimetric analysis was performed with different concentrations of the plant extract incorporated in universal culture bottles containing broth, sample and carbon steel coupon. The setup was incubated at 20ºC, 30ºC and 40ºC for 7 days and for 14 days. The least corrosion rate (CR) at 20ºC, 30ºC and 40ºC for the 7 days test were 1.446mp/y (80mg/ml PAAE); 27.558mp/y (5 mg/mlLeu+20 mg/ml PAAE) and 5.134 mp/y (80 mg/ml PAAE) with corresponding inhibition efficiency (IE) of 81.92, 87.750 and 80.91 respectively. For the 14 days, the CR values at 20ºC, 30ºC and 40ºC were: 3.192mp/y (5mg/mlLeu+20mg/ml PAAE); 1.458 mp/y (5 mg/mlLeu + 20 mg/ml PAAE) and 117.345mp/y (5 mg/mlLeu + 20 mg/ml PAAE) with corresponding IE of 86.09, 83.87 and 98.89 respectively. The results obtained show that the extract could be considered as a good inhibitor for the biocorrosion of carbon steel mediated by acid producing bacteria.

Determination of Bacterial contamination from Well water

Background: Water is one of the most basic needs of life. 90% of the groundwater accounts for the world’s freshwater resources, used for irrigation, industry, and human consumption. Well water is considered as the sole source of drinking water in many regions. The water should be checked regularly to determine bacterial contamination in order to prevent water born bacterial diseases. This study was performed to evaluate the microbial quality of the water from the wells used for drinking purpose. Method: In this cross-sectional study, twenty water samples from ten different wells around the agricultural area were collected in a 200ml capacity sterile container, transported to the laboratory and examined for presumptive coliforms by multiple fermentation tube test. The presumptive coliform count per 100 ml of water was determined using the probability table. Bacteria were then identified using conventional methods. Results: All samples were contaminated with bacteria, and the most predominant bacteria isolated were Klebsiella pneumoniae (40%), followed by Pseudomonas aeruginosa (26%) and E.coli (13%). Of the ten wells tested, seven well water samples were found to be excellent, one satisfactory and two were unsatisfactory. No pathogenic bacteria were seen in any of the samples. Conclusion: Before consumption of water, it should be adequately boiled, or filtered to prevent the incidence of water-borne diseases. Regular screening for bacterial contaminants is necessary in reducing the contamination and supplying safe drinking water.

Bacteriological Quality of the Mangrove Oyster (Crassostrea rhizophorae) in the Swamp of Mestizo - Cordoba (Colombia)

Objectives: To determine the bacteriological quality of the mangrove oyster and its aquatic environment, such as a risk factor in public health, through the consumption of these products from the natural environment. Materials and Methods: Data were collected about 60 samples of oysters and the surrounding water, between June and November 2004. Using the indirect method of counting multiple fermentation tubes, we estimated the concentration of bacteria indicators of total and fecal coliform contamination. The indicators of the bacteriological quality of the oysters presented a minimum of ≤ 3 NMP.100 mL-1 and a maximum of 46 × 104 MPN.100 mL-1 of total coliforms, fecal coliforms showed a seasonal variation in concentrations between ≤3 NMP.100 mL-1 and 2 × 103 MPN.100 mL-1 . Findings: The analysis of water samples recorded a range of concentration of coliforms from ≤ 3 NMP.100 mL-1 to 3.9 × 105 NMP.100 mL-1 and for fecal coliforms it ranged from ≤ 3 NMP.100 mL-1 to 7 × 103 MPN.100 mL-1 . This study suggests that there exists a directly proportional relationship between the bacteriological quality of the mangrove oyster Crassostrea rhizophorae and the water quality of the environment, by its status filtering, which contributes a factor of risk to public health, the consumption of this food, especially if the consumption is done in a direct way. Applications/recommendations: the potentiality of the Bay of Mestizo, Colombia, for the development of a sustainable aquaculture of the mangrove oyster (Crassostrea rhizophorae), requires baseline studies on various environmental and social aspects which will lay the basis for the socio-economic development of this region. Keywords: Molluscs, total coliforms, fecal coliforms, sustainable aquaculture, public health.

Nutrient Content, Protein Fractionation, and Utilization of Some Beans as Potential Alternatives to Soybean for Ruminant Feeding

This experiment aimed to determine nutrient content, protein fraction, and in vitro rumen fermentation of some alternative beans in comparison to soybean. Samples used were napier grass, soybean, redbean, groundnut, pigeonpea, cowpea, bambarabean, and mungbean. Samples were determined for their proximate composition, Van Soest’s fiber fraction, and Cornell protein fraction. The samples were subsequently evaluated for their fermentation characteristics and digestibility by using a two-stage in vitro rumen fermentation technique, maintained at 39 oC for 2 × 48 h. The in vitro incubation was performed in three consecutive runs by following a randomized complete block design in which each sample per run was represented by four fermentation tubes. Results revealed that all experimental beans contained high crude protein (CP), i.e. above 200 g/kg dry matter (DM), but only soybean and groundnut had CP contents higher than 300 g/kg DM. Redbean had the lowest crude fiber and acid detergent fiber contents among the beans. Soybean contained high proportion of rapidly degraded CP fraction, but low in slowly degraded and unavailable CP fractions. High proportion of slowly degraded CP fraction was found in redbean and bambarabean. Redbean, pigeonpea, cowpea, and mungbean were better than soybean, groundnut, and bambarabean with regard to DM degradability and DM digestibility values (P<0.05). Concentration of total VFA was the highest in the incubation of redbean. It was concluded that groundnut, redbean, pigeonpea, cowpea, and mungbean have the potency to be used to substitute soybean for ruminant feeding.

Potential Links between Irrigation Water Microbiological Quality and Fresh Vegetables Quality in Upper East Region of Ghana Subsistence Farming

Potential links between irrigation water microbiological quality and fresh vegetables quality in subsistence farming in Tono in the Upper East Region of Ghana were investigated. Water samples from Tono and Nanglakinia dam and six different types of vegetables (collected from Nanglakinia, Bonia, Korania), irrigated with this water were analysed for microbiological qualities. The study was carried out within a month. Bacillus cereus, Clostridium perfringes, Escherichia coli, Salmonella and Shigella, Streptococcus spp, Staphylococcus spp and Yeast sp. were enumerated using plate count method while Total coliform bacteria were enumerated using Multiple Fermentation Tube Method. In water samples, Bacillus cereus counts ranged from 34 x 10 5 to 49 x 10 5 cfu/ml , Staphylococcus spp. counts ranged from 1 x 10 cfu/ml to 26 x 10 cfu/ml. Clostridium perfringes had bacteria counts 55 x 10 5 cfu/ml to 66 x 10 5 cfu/ml. Escherichia coli counts ranged between 51 x 10 cfu/ml to 79 x 10 cfu/ml. Salmonella spp. ranged from 8 x 10 cfu/ml to 47 x 10 cfu/ml. Yeast sp. also had counts ranging from 21 x 10 5 cfu/ml to 70 x10 5 cfu/ml. Total coliform counts ranged from 460 MPN/100ml to >1100 MPN/100 ml. In the vegetable samples, Bacillus cereus counts ranged from 3 x 10 cfu/g to 74 x 10 cfu/g. Staphylococcus spp. counts ranged from 0 to 21 Original Research Article Adetunde LA et al.; ARRB, 6(6): 347-354, 2015; Article no.ARRB.2015.094 348 x 10 5 cfu/g, Clostridium perfringes counts ranged from 37 x 10 5 cfu/g to 80 x 10 5 cfu/g. Escherichia coli counts ranged from 4 x 10 cfu/g to 80 x 10 cfu/g. Salmonella spp. counts ranged from 0 to 70 x 10 cfu/g. Yeast sp. also had counts ranging from 0 to 75 x 10 cfu/g. Streptococcus spp. was also tested for but there were no bacteria counts recorded. The microbial loads found in the water were similar to those on the fresh produce which showed potential links of the organisms.

Disinfection of raw wastewater and activated sludge effluent using Fenton like reagent.

Background and objectivesWater shortage problems have led to find either new water resources or improve wastewater treatment technologies in order to reuse. Due to less performance of previous units in microbial removal, disinfection has become a necessary step in wastewater treatment plants. In the present study performance of hydrogen peroxide (HP) and modified Fenton’s reagent (HP + Cu++) was considered for the disinfection of raw wastewater (RW) and activated sludge effluent (ASE).Materials and methodsPlastic containers of 10-liter volume each were used for RW and ASE sampling. Microbiological analyses of the RW and ASE were performed in triplicate; before and after the disinfection process. Fecal coliforms were analyzed by the direct (without enrichment) multiple fermentation tube procedure.ResultsThe results showed that using HP alone did not have any significant disinfection capability. In RW and ASE, the highest dose used in this study could reduce fecal coliforms (FC)s by only 1.54 and 1.16 log-inactivation, respectively. However, Maximum removal efficiency of modified Fenton in RW and ASE was 4.63 and 3.41 log-inactivation, respectively. The results suggested that Cu++ ions used in combination with H2O2 produced very rigorous synergistic effect, and HP disinfection capacity increased significantly.ConclusionHydrogen peroxide, when applied alone, was not successful in disinfecting of either RW or ASE, and neither the WHO guideline nor the Iranian standard could be met. However, modified Fenton showed very significant disinfection potential and could reduce FCs under World Health Organization (WHO) guideline and Iranian national standard for agricultural irrigation.

EVALUATING EFFICIENCY OF RADIO WAVES FOR MICROBIAL REMOVAL IN WATER SAMPLES

The most common used methods for water disinfection were chemicals like chlorine, ozonation, ultraviolet radiation, membrane processes, etc. Water disinfection using irradiation techniques is new in water treatment industry which has been developed recently. The aim of the present study was to investigate radio frequency (RF) efficiency for the inactivation of total coliform (TC), fecal coliform, and heterotrophic bacterial count of water pellets. Tap water samples were taken from School of Public Health, Tehran University of Medical Sciences and irradiated using hydropad device, steam KLEAR model S-38 (1.2 W and frequency of 120-200 kHz). Microbial concentration was measured in cycles 1, 5, 10, 15, 20, 25, 30, 35, and 40 in 1 and 2 h contact time. Indicator bacteria were counted using plate count method and multiple fermentation tube technique. According to the microbial results, after 40 cycles and without chlorine residual, TC, fecal coliform, and heterotrophic bacteria were reduced by 86, 90, and 85%, while after 15 cycles and 0.8 mg/l chlorine residual, removal rate was 89, 91, and 89%, respectively. Furthermore, it was observed that after 2 h of contact time, TCs, fecal coliforms, and heterotrophic plate count were reduced by 78.2, 80, and 60%, respectively. Although RF efficiency in water disinfection has not been studied, our findings suggested its possible use due to more than 75% efficiency. From the standpoint of practical use, more studies should be done, especially to find a fine synergist agent, determining power, frequency, and suitable contact time and also the method should be modified.

Fermentation Tube Test Statistics for Indirect Water Sampling

By aiming at correction of the existing standards of the Fermentation Tube Test (FTT) this article critically reviews one of the oldest statistical methodologies used in sanitary engineering clearly relevant to health science. The common practice of water works is to perform the FTT on water samples for detecting fecal bacteria contamination in raw water prior to technological processing. Analysis of the Fermentation Tube Test (FTT) statistics presented in the article is to support a hypothesis that “standard FTT procedures may not be compatible with the statistical tables of FTT in the Standard Methods (1998, 2005)”. The inconsistency can be seen from the observation that the standard FTT procedures require subsequent dilution of water samples, which implies the indirect sampling. At the same time, the Standard Methods (1998, 2005) statistical tables used for FTT interpretations result from the assumption of the direct water sampling. In the article a statistical context of the Most Probable Number of bacteria, MPN, for actual, i.e. indirect, procedures of water sampling is described. Theoretical background of the inconsistency is explained and the remedy proposed by means of a new formula for calculating Most Probable Number of Bacteria consistent with actual indirect sampling procedures. The inconsistency is illustrated with simple but realistic example. As the ultimate result of the research it is proposed to modify the existing MPN tables and thus eliminate the inconsistency between the standard FTT procedures and the FTT tables published in the Standard Methods (1998, 2005) and ISO (1988) standards.

Non albicans Candida species: its isolation pattern, species distribution, virulence factors and antifungal susceptibility profile

Background: The change in epidemiology and antifungal susceptibility has generated interest of Clinical Microbiologists in identification of Candida up to species level along with antifungal susceptibility pattern. Non-albicans Candida (NAC) has emerged as an important opportunist pathogen. Extracellular hydrolytic enzymes are one of the important virulence attributes of Candida species. Aims & Objective: The present study aimed to determine the species distribution, virulence factors and antifungal susceptibility profile of NAC spp. isolated from various clinical specimens. Material and Methods: Speciation of Candida was done by assessing the germ tube formation, assimilation and fermentation of sugars and colony color on HICHROM Candida agar. In-vitro extracellular hydrolytic enzymes production in NAC spp. was assessed. Antifungal susceptibility testing of the isolates was performed by Hicomb minimum inhibitory concentration (MIC) test. Results: Majority of the isolates were obtained from urine sample (35.6%). C. tropicalis (29.4%) was the major isolate. Maximum extracellular hydrolytic enzymes activity was seen in C. tropicalis. A total of 79 (27.3%) isolates were resistant to fluconazole. Amphotericin B resistance was noted in 17 (5.8%) isolates. Conclusion: NAC spp. cannot be overlooked as mere containment or non-pathogenic commensals as most of them show reduced susceptibility to commonly used antifungal drugs. Extracellular hydrolytic enzymatic activity of NAC Spp. would be an important tool to prove the relation between the infective species of Candida and infection.

Microbial quality of well water from rural and urban households in Karnataka, India: A cross-sectional study

The objective of this study was to evaluate the microbial quality of the well water used as a drinking source in urban and rural households. A total of 80 household well water samples were analyzed by the multiple fermentation tube method to determine the presumptive coliform count/most probable number of coliforms, and the isolates were identified using standard procedures, followed by susceptibility testing. Fecal indicator organisms, including Escherichia coli and Enterococcus spp. were isolated from 22 (27.5%) samples, and the majority (92.5%) of the water sources were contaminated with coliforms. A total of 170 bacterial isolates were obtained, including coliforms (70%), Enterococcus spp. (1.8%) and saprophytes (28.2%). A significant number of isolates were multi-drug resistant, which is a cause of concern. A comparison of the microbial quality of the water between urban and rural households revealed no significant differences. It might be prudent to monitor the bacteriological quality of well water at the source in addition to resistance profiles of the isolates.

Rumen microbial volatile fatty acids in relation to oxidation reduction potential and electricity generation from straw in microbial fuel cells

This study determined volatile fatty acids (VFA) from ruminal microbial fermentation in relation to oxidation reduction potential (ORP) and electricity generation from straw in microbial fuel cells. The effect of substrate straw to grain ratio on gas production, VFA, pH, and ORP during rumen microbial incubation with or without the presence of protozoa was evaluated. Increasing straw relative to grain in the substrate mixture resulted in lower gas levels, VFA, and ORP, but a higher pH. The ratio of acetate to propionate increased when more straw was included in the mixture. When straw was the sole substrate, the ratio of acetate to propionate decreased in response to increasing straw addition to the fermentation tubes. A correlation analysis showed that ORP values were inversely correlated with the ratio of acetate to propionate, with a coefficient of −0.712. When straw was added to MFCs, the VFA increased almost two-fold after inoculation with ruminal fluid. Maximum power density reached 0.00309 mW/m2 following a second transfer of spent fermentation fluid to fresh MFCs. Acetate was the major VFA in the straw-fed MFC, followed by propionate and butyrate. Their concentrations were negatively associated with voltage output. However, the acetate to propionate ratio was positively linked to electricity production. The results illustrate that the VFA profile during ruminal microbial fermentation could be influential on ORP and electricity generation in MFCs. The results provide evidence that native fiber and straw could be utilized for electricity production by ruminal microbial MFCs.

Fermentation tube test statistics for direct water sampling and comments on the Thomas formula

This article describes a new interpretation of the Fermentation Tube Test (FTT) performed on water samples drawn from natural waters polluted by faecal bacteria. A novel general procedure to calculate the Most Probable Number of bacteria (MPN) in natural waters has been derived for the FTT for both direct and independent repetitive multiple water sampling. The generalization based on solving the newly proposed equation allows consideration of any a priori frequency distribution g(n) of bacterial concentration in analysed water as opposed to the unbounded uniform a priori distribution g(n) assumed in the standard procedures of the Standard Methods of Examining Water and Wastewater and ISO 8199:1988. Also a statistical analysis of the Thomas formula is presented. It is demonstrated that the Thomas formula is highly inaccurate. The authors propose, therefore, to remove the Thomas formula from the Standard Methods of Examining Water and Wastewater and ISO 8199:1988 altogether and replace it with a solution of the proposed generalized equation.

Effects of supplemental zinc concentration on cellulose digestion and cellulolytic and total bacterial numbers in vitro

Effects of various zinc (Zn) concentrations on cellulose digestion and cellulolytic and total bacterial numbers were studied in vitro. All fermentation tubes were inoculated with a 1:10 dilution of whole rumen contents and used either 0.0075 or 0.015 g/ml purified cellulose as substrate. When Zn was added at six different concentrations: 5, 10, 15, 20, 25 and 50 μg/ml, using either 0.0075 or 0.015 g/ml cellulose, the 50 μg/ml concentration reduced cellulose digestion ( P<0.01) at 24 h of incubation. However, cellulose digestion was similar to the control tubes at 48 h. At 24 h, addition of Zn at 50 μg/ml to the medium containing 0.0075 g/ml cellulose lowered cellulose digestion ( P<0.016), but did not affect cellulolytic and total bacterial concentrations. By 48 h, cellulolytic bacterial concentrations in the control tubes were lower ( P<0.001) than in the Zn supplemented tubes. Total bacterial concentrations were also lower ( P=0.076) for control tubes. Using 0.015 g/ml cellulose and Zn concentrations of 0, 50, 100 and 150 μg/ml, cellulose digestion after 24 h was lower than the control for all tubes with added Zn ( P<0.01). By 48 h, cellulose digestion was similar in tubes containing 0 and 50 μg/ml concentrations of Zn, while digestion remained lower with concentrations of 100 and 150 μg/ml ( P<0.01). After 72 h, only the 150 μg/ml Zn concentration had less cellulose digested ( P<0.05). Final pH values followed a similar pattern: the higher the Zn concentration, the less decrease in pH. Concentrations of cellulolytic bacteria were lower ( P<0.001) in all tubes with Zn after 24 h incubation, but their concentration in the control tubes decreased markedly between 24 and 48 h, presumably due to low pH and substrate limitation. No differences were observed in total bacterial concentrations at any fermentation time period. The decreased cellulolytic bacterial concentration in the tubes with high Zn levels may be due to decreased utilization of cellulose by the bacteria, rather than a toxic effect of high Zn on the bacteria. Possibly Zn has an inhibitory effect on the cellulolytic enzymes produced by the bacteria.