John J. Classen

Aspergillus niger absorbs copper and zinc from swine wastewater

Wastewater from swine confined-housing operations contains elevated levels of copper and zinc due to their abundance in feed. These metals may accumulate to phytotoxic levels in some agricultural soils of North Carolina due to land application of treated swine effluent. We evaluated fungi for their ability to remove these metals from wastewater and found Aspergillus niger best suited for this purpose. A. niger was able to grow on plates amended with copper at a level five times that inhibitory to the growth of Saccharomyes cerevisiae. We also found evidence for internal absorption as the mechanism used by A. niger to detoxify its environment of copper, a property of the fungus that has not been previously exploited for metal bioremediation. In this report, we show that A. niger is capable of removing 91% of the copper and 70% of the zinc from treated swine effluent.

Nutrient recovery from swine lagoon water by Spirodela punctata.

Spirodela punctata 7776, the best duckweed strain in total protein production selected from in vitro screening experiments with synthetic swine lagoon water medium was examined for N and P recovery. It has shown a capability to grow in and to remove N and P from synthetic swine lagoon water with high N (240 mg NH4 N/l) and P (31.0 mg PO4 P/l) levels. A lag period of approximately 96 h was observed before the duckweed started to grow. During the lag period, utilization of N and P by the duckweed was very slow. The rates of N and P uptake, and duckweed growth increased with the increase of the initial N and P concentrations in the medium. The highest rates of N and P uptakes, and duckweed growth observed in this study were 0.955. 0.129 mg/l-h, and 1.33 g/m2-h (or 31.92 g/m2-day), respectively. The N:P ratio in swine lagoon water is adequate for growing the duckweed.

In vitro selection of duckweed geographical isolates for potential use in swine lagoon effluent renovation

Plant-based systems for nutrient sequestration into valuable biomass have the potential to help avoid the environmental problems associated with the disposal of large volumes of animal waste. The objective of this study was to select superior duckweed (Lemnaceae) genotypes for the utilization of nutrients in animal wastes. A two-step protocol was used to select promising duckweed geographic isolates to be grown on swine lagoon effluent. Forty-one geographic isolates from the worldwide germplasm collection were used in an in vitro screening test, because they were noted to be fast-growing genotypes during routine collection maintenance. In vitro screening was accomplished by growing geographic isolates on a synthetic medium that approximated swine lagoon effluent in terms of nutrient profile, total ionic strength, pH, and buffering capacity. Large differences among geographic isolates were observed for wet weight gain during the 11-day growing period, percent dry weight, and percent protein in dry biomass. Total protein production per culture jar differed 28-fold between the most disparate of the 41 geographic isolates and was the variable used for selection of superior geographic isolates. The challenge of eight of the 41 geographic isolates with full-strength swine lagoon effluent in the greenhouse led to the selection of three that are promising as genotypes to be grown on lagoon effluent.

NUTRIENT REMOVAL FROM SWINE LAGOON LIQUID BY LEMNA MINOR 8627

Nitrogen and phosphorus removal from swine lagoon liquid by growing Lemna minor 8627, a promising duckweed identified in previous studies, was investigated under in vitro and field conditions. The rates of nitrogen and phosphorus uptake by the duckweed growing in the in vitro system were as high as 3.36 g m–2 day–1 and 0.20 g m–2 day–1, respectively. The highest nitrogen and phosphorus removal rates in the field duckweed system were 2.11 g m–2 day–1 and 0.59 g m–2 day–1, respectively. The highest observed duckweed growth rate was close to 29 g m–2 day–1 in both conditions. Wastewater concentrations and seasonal climate conditions had direct impacts on the duckweed growth and nutrient removal in outdoor tanks. The rate of duckweed production in diluted swine lagoon liquid increased as the dilution rate increased. Duckweed assimilation was the dominant mechanism for nitrogen and phosphorus removal from the swine lagoon liquid when the nutrient concentration in the wastewater was low, but became less important as nutrient concentration increased. Reasonably high light intensity and a longer period of warm temperature could result in a higher growth rate for the duckweed. Pre–acclimation of the duckweed with swine lagoon liquid could accelerate the start–up of a duckweed system to remove nutrients from the wastewater by preventing the lag phase of duckweed growth.

AMMONIA EMISSIONS FROM ANIMAL FEEDING OPERATIONS

An accepted definition of antibiotic resistance as presented in 1998 by the Institute of Medicine is “a property of bacteria that confers the capacity to inactivate or exclude antibiotics, or a mechanism that blocks the inhibitory or killing effects of antibiotics, leading to survival despite exposure to antimicrobials (Jjemba and Robertson, 2002). The occurrence of microbial pathogens demonstrating “resistance” to adverse stressors threatening their very survival is not a new (Phillips et al., 2004; WHO, 2001). Bacteria have developed mechanisms for protection in a wide range of environments over time, some of which are currently better understood due to advances in scientific methods and analytical techniques. The development of antibiotics for human and animal use dates back many years; perhaps most notable was Alexander Flemming’s creation of penicillin in 1928 (GIH, 2000). Many infectious diseases that once caused increasing mortality and morbidity rates among humans and animal populations have been effectively managed as a result of having antibiotics and pharmaceuticals available in health care management. Despite these positive outcomes, both the widespread usage and lack of prudent use of antibiotics have caused global concerns about increasing incidences of antibiotic resistance properties and strains of resistant organisms. Concerns have also increased with the recognition of greater interconnectedness between humans, animals and the environment throughout the global community. Further complicating this issue are the economic interests associated with industrial progress; hazards considered low-level and long-term seldom gain the same attention as that of crisis scenarios; and incremental knowledge about public health concerns often raises troubling questions about risk and response (GIH, 2000).

NUTRIENT REMOVAL FROM SWINE LAGOON EFFLUENT BY DUCKWEED

ABSTRACT. Three duckweed geographic isolates were grown on varying concentrations of swine lagoon effluent in a greenhouse to determine their ability to remove nutrients from the effluent. Duckweed biomass was harvested every other day over a 12-day period. Duckweed biomass production, nutrient loss from the swine lagoon effluent, and nutrient content of duckweed biomass were used to identify effluent concentrations/geographic isolate combinations that are effective in terms of nutrient utilization from swine lagoon effluent and production of healthy duckweed biomass. When Lemna minor geographic isolate 8627 was grown on 50% swine lagoon effluent, respective losses of TKN, NH 3 -N, TP, OPO 4 -P, TOC, K, Cu, and Zn were 83, 100, 49, 31, 68, 21, 28, and 67%.

ROLE OF INTERNAL NUTRIENT STORAGE IN DUCKWEED GROWTH FOR SWINE WASTEWATER TREATMENT

The objective of this study was to investigate the relationship of the nutrient content of duckweed biomass to duckweed growth in swine wastewater. Batch tests of Spirodela punctata 7776, the selected strain for highest total protein production, were conducted in an environment-controlled growth chamber at 24°C and 16 h of light per day. A prolonged growth period was observed after the nutrients in the medium were exhausted, indicating that duckweed could use its stored nutrients for growth. Prediction of growth using medium concentration as an independent variable was deemed unsuitable to describe this growth. Throughout the 30-day growing period, nitrogen and phosphorus content in the biomass varied from 59.7 to 19.7 mgN/gbiomass and from 14.8 to 6.8 mgP/gbiomass (dry weight basis), respectively. The relationship between biomass nitrogen content and specific growth rate of Spirodela punctata 7776 was found to follow Monod-type kinetics with .max of 0.24 gN/gbiomass/day and KN of 28.8 mgP/gbiomass. Reduced growth rate was observed in the duckweed culture with high duckweed density (mass per unit area). Effects of the duckweed density on growth rate and nutrient uptake are modeled and discussed.

Mechanisms of dinitrogen gas formation in anaerobic lagoons

Abstract Anaerobic lagoons have been widely used to treat agricultural waste and waste from small municipalities for many years. Oxidation of ammonia is generally assumed to not occur in such lagoons because of their anaerobic environment. Nitrification, the most likely process that would lead to ammonia oxidation, has not been considered a significant process in anaerobic lagoons because of the negligible concentrations of dissolved oxygen measured in these systems. Therefore observed nitrogen losses are usually assumed to be due to ammonia volatilization. However, in field studies of primary swine waste lagoons in the south-eastern US Coastal Plain, rates of dinitrogen (N 2 ) gas production have been observed to be much greater than rates of NH 3 volatilization. This paper discusses possible mechanisms that could explain observations of N 2 gas generation in anaerobic waste lagoons. Chemical and microbial reactions have been documented that combine ammonia with nitrite, or nitrous acid, to form N 2 under anaerobic conditions. Nitrification and denitrification reactions have also been observed under microaerobic conditions. Each of these reactions requires low levels of oxygen for the initial nitrification of ammonia to nitrite. Diffusion rates of oxygen through the lagoon surface appear to be adequate to allow enough nitrite formation to explain observed N 2 fluxes.

The effects of vermicompost on field turnips and rainfall runoff

Vermicompost made from separated swine waste solids (0, 10, or 20% by volume of soil) was applied to turnips in small field plots during four growing seasons to determine the effect on plant growth, runoff volume and nutrients in runoff. The effect of nitrogen fertilizer was controlled by supplementing half the plots with inorganic nitrogen to balance the nitrogen fertilizer recommendations for turnips. Vermicompost addition increased fresh weight of fruit and foliage by a factor of two to five and increased dry weight by a factor of three with no increase in nitrogen but higher phosphorus in runoff. Runoff volume was lower in plots that received vermicompost compared to control plots.

A logistic model of subsurface fungal growth with application to bioremediation

Abstract The goal of this research was to determine the potential of the fungal sterol ergosterol as an indicator of fungal biomass and to determine the growth response of the transformed strain of T. virens (GvT6) to added substrate and changes in temperature. Experiments in liquid culture and agar plates containing a rich medium of glucose, yeast extract, and casein (GYEC), or a soil extract medium supplemented with maltose (SE) showed that the ergosterol content of GvT6 was greatest when grown on GYEC agar plates (14.02 mg/g dry biomass). For both media, plate cultures produced higher specific ergosterol values than liquid cultures. Changes in specific ergosterol values over time were generally not significant. A value of 5.41 mg ergosterol / g dry biomass, determined for SE plate cultures, was used to convert ergosterol values to biomass values in growth experiments in soil bioreactors. Data from experiments in soil bioreactors treated with different levels of substrate (0.5–8 mg maltose / g dry soil) at three different temperatures (22, 27, 32°C) showed subsurface growth of GvT6 can be described by the logistic equation. Culture conditions of 32°C and 8 mg/g substrate produced the highest levels of biomass, but growth at 32°C and 4 mg/g substrate was somewhat faster than at the higher substrate level.