Effects of ball milling on biochar adsorption of contaminants in water: A meta-analysis.

Reckless release of contaminants into the environment causes pollution in various aquatic systems on a global scale. Biochar is potentially an inexpensive and environmentally friendly adsorbent for removing contaminants from water. Ball milling has been used to enhance biochar's functionality; however, global analysis of the effect of ball milling on biochar's capacity to adsorb contaminants in aqueous solutions has not yet been done. Here, we conducted a meta-analysis to investigate the effects of ball milling on the adsorption/removal capacity of biochar for contaminants in aqueous solutions, and to investigate whether ball milling effects are related to biochar production, ball milling, and other experimental variables. Overall, ball milling significantly increased biochar adsorption capacity towards both inorganic and organic contaminants, by 69.9% and 561.9%, respectively. This could be attributed to ball milling increasing biochar surface area by 2.05-fold, pore volume by 2.39-fold, and decreasing biochar pH by 0.83-fold. The positive adsorption effects induced by ball milling varied widely, with the most effective being ball milling for 12 to 24 h at 300 to 400 rpm with a biochar:ball mass ratio of 1:100 on biochars produced at 400-550 °C from wood residues. Based on this meta-analysis, we conclude that ball milling could effectively enhance biochar's ability to remove organic and inorganic contaminants from aquatic systems.

Fate of Listeria monocytogenes in bovine manure-amended soil.

The survival and growth of Listeria monocytogenes in soil amended with bovine manure was studied under different environmental conditions of temperature, nutrients, and soil microflora. Autoclaved soil was compared with unautoclaved soil for assessing the influence of competitive soil microflora on the survival of L. monocytogenes. Initial L. monocytogenes cell numbers of 5 to 6 log CFU/g survived for up to 43, 43, and 14 days in manure-amended autoclaved soil at 5, 15, and 21 degrees C, respectively. In manure-amended unautoclaved soil, the pathogen was detectable for up to 43, 21, and 21 days at 5, 15, and 21 degrees C, respectively. L. monocytogenes was inactivated more rapidly in autoclaved soil amended with manure at a manure/soil ratio of 1:10 than in the more dilute (1:100) manure in soil samples at both 15 and 21 degrees C. However, in manure-amended unautoclaved soil, L. monocytogenes survived longer in samples with ratios of 1:10 than in the more dilute (1:100) manure-amended soil. The persistence of L. monocytogenes for several weeks in manure-amended soil suggests listeriae could be transmitted through soil to fresh produce or to shoes, clothing, and hands of field workers, especially during the cold months.

Persistence of enterohemorrhagic Escherichia coli O157:H7 in soil and on leaf lettuce and parsley grown in fields treated with contaminated manure composts or irrigation water.

Outbreaks of enterohemorrhagic Escherichia coli O157:H7 infections associated with lettuce and other leaf crops have occurred with increasing frequency in recent years. Contaminated manure and polluted irrigation water are probable vehicles for the pathogen in many outbreaks. In this study, the occurrence and persistence of E. coli O157:H7 in soil fertilized with contaminated poultry or bovine manure composts or treated with contaminated irrigation water and on lettuce and parsley grown on these soils under natural environmental conditions was determined. Twenty-five plots, each 1.8 by 4.6 m, were used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but treated with contaminated water) and five replication plots for each treatment. Three different types of compost, PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline-stabilized dairy manure compost), and irrigation water were inoculated with an avirulent strain of E. coli O157:H7. Pathogen concentrations were 10(7) CFU/g of compost and 10(5) CFU/ml of water. Contaminated compost was applied to soil in the field as a strip at 4.5 metric tons per hectare on the day before lettuce and parsley seedlings were transplanted in late October 2002. Contaminated irrigation water was applied only once on the plants as a treatment in five plots for each crop at the rate of 2 liters per plot 3 weeks after the seedlings were transplanted. E. coli O157:H7 persisted for 154 to 217 days in soils amended with contaminated composts and was detected on lettuce and parsley for up to 77 and 177 days, respectively, after seedlings were planted. Very little difference was observed in E. coli O157:H7 persistence based on compost type alone. E. coli O157:H7 persisted longer (by > 60 days) in soil covered with parsley plants than in soil from lettuce plots, which were bare after lettuce was harvested. In all cases, E. coli O157:H7 in soil, regardless of source or crop type, persisted for > 5 months after application of contaminated compost or irrigation water.

Reduction of Escherichia coli O157:H7 and Salmonella enterica serovar Enteritidis in chicken manure by larvae of the black soldier fly.

Green fluorescent protein-labeled Escherichia coli O157:H7 and Salmonella enterica serovar Enteritidis were inoculated at 10(7) CFU/g into cow, hog, or chicken manure. Ten- or 11-day-old soldier fly larvae (Hermetia illucens L.) (7 to 10 g) were added to the manure and held at 23, 27, or 32 degrees C for 3 to 6 days. Soldier fly larvae accelerated inactivation of E. coli O157:H7 in chicken manure but had no effect in cow manure and enhanced survival in hog manure. The initial pH values of the hog and chicken manure were 6.0 to 6.2 and 7.4 to 8.2, respectively, and it is surmised that these conditions affected the stability of the larval antimicrobial system. Reductions of E. coli O157:H7 populations in chicken manure by larvae were affected by storage temperature, with greater reductions in samples held for 3 days at 27 or 32 degrees C than at 23 degrees C. Pathogen inactivation in chicken manure by larvae was not affected by the indigenous microflora of chicken manure, because Salmonella Enteritidis populations in larvae-treated samples were approximately 2.5 log lower than control samples without larvae when either autoclaved or nonautoclaved chicken manure was used as the contaminated medium during 3 days of storage. Extending the storage time to 6 days, larvae again accelerated the reduction in Salmonella Enteritidis populations in chicken manure during the first 4 days of storage; however, larvae became contaminated with the pathogen. After 2 days of feeding on contaminated manure, Salmonella Enteritidis populations in larvae averaged 3.3 log CFU/g. Populations decreased to 1.9 log CFU/g after 6 days of exposure to contaminated chicken manure; however, the absence of feeding activity by the maggots in later stages of storage may be responsible for the continued presence of Salmonella Enteritidis in larvae. Transfer of contaminated larvae to fresh chicken manure restored feeding activity but led to cross-contamination of the fresh manure.

Fate of Salmonella enterica serovar Typhimurium on carrots and radishes grown in fields treated with contaminated manure composts or irrigation water.

Three different types of compost, PM-5 (poultry manure compost), 338 (dairy cattle manure compost), and NVIRO-4 (alkaline-pH-stabilized dairy cattle manure compost), and irrigation water were inoculated with an avirulent strain of Salmonella enterica serovar Typhimurium at 10(7) CFU g(-1) and 10(5) CFU ml(-1), respectively, to determine the persistence of salmonellae in soils containing these composts, in irrigation water, and also on carrots and radishes grown in these contaminated soils. A split-plot block design plan was used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but with contaminated water applied) and five replicates for a total of 25 plots for each crop, with each plot measuring 1.8 x 4.6 m. Salmonellae persisted for an extended period of time, with the bacteria surviving in soil samples for 203 to 231 days, and were detected after seeds were sown for 84 and 203 days on radishes and carrots, respectively. Salmonella survival was greatest in soil amended with poultry compost and least in soil containing alkaline-pH-stabilized dairy cattle manure compost. Survival profiles of Salmonella on vegetables and soil samples contaminated by irrigation water were similar to those observed when contamination occurred through compost. Hence, both contaminated manure compost and irrigation water can play an important role in contaminating soil and root vegetables with salmonellae for several months.

Fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and onions grown in an environmentally controlled growth chamber.

Studies were done to determine the fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and green onions grown in an environmentally controlled growth chamber. Commercial dairy cattle manure compost was inoculated with a five-strain mixture of green fluorescent protein-labeled E. coli O157:H7 at 10(7) CFU g(-1) and mixed with unsterilized Tifton sandy loam soil at a ratio of 1:5. Baby carrot or green onion seedlings were planted into the manure compost-amended soil in pots, and soil samples surrounding the plant, edible carrot roots and onion bulb samples, and soil immediately beneath the roots were assayed for E. coli O157:H7 in triplicate at weekly intervals for the first 4 weeks, and every 2 weeks for the remainder of the plant growth cycle (up to 3 months). E. coli O157:H7 cell numbers decreased within 64 days by 3 log CFU/g in soil and soil beneath the roots of green onions and by more than 2 log CFU/g on onions. E. coli O157:H7 survived better during the production of carrots, with a 2.3-log CFU/g reduction in soil and a 1.7-log CFU/g reduction on carrots within 84 days. These results indicate that the type of plant grown is an important factor influencing the survival of E. coli O157:H7 both on the vegetable and in the soil in which the vegetable is grown.

Persistence of Salmonella enterica serovar typhimurium on lettuce and parsley and in soils on which they were grown in fields treated with contaminated manure composts or irrigation water.

There are many sources of pathogen contamination of vegetable crops in the field that include manure used as fertilizer and irrigation water. An avirulent strain of Salmonella enterica serovar Typhimurium was added to three different types of composts-PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline stabilized dairy manure compost)-and irrigation water at 10(7) colony forming units (cfu)/g and 10(5) cfu/mL, respectively, to determine under field conditions the persistence of salmonellae in soils treated with these composts or irrigation water, and also on leaf lettuce and parsley grown on such treated soil. Contaminated compost was applied to soil in the field as a strip at a rate of 4.5 metric tons/hectare on the day before lettuce and parsley seedlings were transplanted. Contaminated irrigation water was applied only once on the plants at the rate of 2 liters per plot on the same day after the seedlings were transplanted. Twenty-five plots, each measuring 1.8 x 4.6 meters, were used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but applied with contaminated water) and five replication plots for each treatment. Salmonella persisted for 161 and up to 231 days in soils amended with contaminated composts on which lettuce and parsley, respectively, were grown, and was detected for up to 63 days and 231 days on lettuce and parsley, respectively. The type of contaminated compost had minimal effect on the persistence of S. Typhimurium in soil. Occurrence of Salmonella on vegetables and survival in soil on which these vegetables were grown, irrespective of source of contamination through irrigation water or compost, were similar, suggesting both contaminated manure compost and irrigation water can play important roles in contaminating soil and vegetables with Salmonella for an extended period of time.

Control of Listeria monocytogenes on turkey frankfurters by generally-recognized-as-safe preservatives.

Generally-recognized-as-safe chemicals applied to the surfaces of turkey frankfurters were evaluated for their ability to reduce populations of or inhibit the growth of Listeria monocytogenes. Frankfurters were treated prior to inoculation by dipping for 1 min in a solution of one of four preservatives (sodium benzoate, sodium propionate, potassium sorbate, and sodium diacetate) at three different concentrations (15, 20, and 25% [wt/vol]), with < 0.3% of the preservative being present for each frankfurter. Subsequently, 0.1 ml of a five-strain mixture of L. monocytogenes (10(6) CFU/ml) was used to surface inoculate each frankfurter separately in a sterile stomacher bag. Inoculated frankfurter bags were held at 4, 13, and 22 degrees C, and L. monocytogenes cells were enumerated at 0, 3, 7, 10, and 14 days of storage. The results of this study revealed that at all three concentrations of all four preservatives, the initial populations of L. monocytogenes decreased immediately by 1 to 2 log10 CFU/g. After 14 days of storage at 4 degrees C, L. monocytogenes counts for all treated frankfurters were 3 to 4 log10 CFU/g less than those for the untreated frankfurters. After 14 days of storage at 13 degrees C, L. monocytogenes counts for frankfurters treated with 25% sodium benzoate or 25% sodium diacetate were 3.5 to 4.5 log10 CFU/g less than those for untreated frankfurters, and those for frankfurters treated with 25% sodium propionate or 25% potassium sorbate were 2.5 log10 CFU/g less than those for untreated frankfurters. In all instances, the degree of growth inhibition was directly proportional to the concentration of the preservative. Only frankfurters treated with 25% sodium diacetate or sodium benzoate were significantly inhibitory to L. monocytogenes when held at 22 degrees C for 7 days or longer. Interestingly, the untreated frankfurters held at 22 degrees C were spoiled within 7 days, with copious slime formation, whereas there was no evidence of slime on any treated frankfurters after 14 days of storage.

Effect of selected generally recognized as safe preservative sprays on growth of Listeria monocytogenes on chicken luncheon meat.

The ability of selected generally recognized as safe (GRAS) chemical preservatives to reduce populations or inhibit growth of Listeria monocytogenes on chicken luncheon meat was evaluated. Slices of luncheon meat were treated by evenly spraying onto their surfaces 0.2 ml of a solution of one of four preservatives (sodium benzoate, sodium propionate, potassium sorbate, and sodium diacetate) at one of three different concentrations (15, 20, or 25% [wt/vol]). Each slice was then surface inoculated with a five-strain mixture of 10(5) CFU of L. monocytogenes per ml, held at 4, 13, or 22 degrees C, and assayed for L. monocytogenes immediately after inoculation and at 3, 7, 10, and 14 days of storage. Initial reductions of L. monocytogenes populations ranged from 0.78 to 1.32 log10 CFU g(-1) at day 0 for sodium benzoate- or sodium diacetate-treated meat, whereas reductions for the sodium propionate or potassium sorbate treatments were only 0.14 to 0.36 log10 CFU g(-1). After 14 days of storage at 4 degrees C, L. monocytogenes populations on all treated slices were 1.5 to 3 log10 CFU g(-1) less than on the untreated slices. At 13 degrees C and after 14 days of storage, L. monocytogenes populations were 3.5 and 5.2 log10 CFU g(-1) less on luncheon meat slices treated with 25% sodium benzoate or 25% sodium diacetate, respectively, and ca. 2 log10 CFU g(-1) less when treated with 25% sodium propionate or 25% potassium sorbate than on untreated control slices. Only sodium diacetate was highly inhibitory to L. monocytogenes on meat slices held at 22 degrees C for 7 days or longer. Untreated luncheon meat held at 22 degrees C was visibly spoiled within 10 days, whereas there was no evidence of visible spoilage on any treated luncheon meat at 14 days of storage.