Cultivation of Chlorella sp. HS2 using wastewater from soy sauce factory.

Incorporation of wastewater from industrial sectors into the design of microalgal biorefineries has significant potential for advancing the practical application of this emerging industry. This study tested various food industrial wastewaters to assess their suitability for microalgal cultivation. Among these wastewaters, defective soy sauce (DSS) and soy sauce wastewater (SWW) were chosen but DSS exhibited the highest nutrient content with 13,500 ppm total nitrogen and 3051 ppm total phosphorus. After diluting DSS by a factor of 50, small-scale cultivation of microalgae was conducted to optimize culture conditions. SWW exhibited optimal growth at 25-30 °C and 300-500 µE m-2 s-1, while DSS showed optimal growth at 30-35 °C. Based on a 100-mL lab-scale and 3-L outdoor cultivation with an extended cultivation period, DSS outperformed SWW, exhibiting higher final biomass productivity. Additionally, nutrient-concentrated nature of DSS is advantageous for transportation at an industrial scale, leading us to select it as the most promising feedstock for microalgal cultivation. With further optimization, DSS has the potential to serve as an effective microalgal cultivation feedstock for large-scale biomass production.

Stepwise treatment of undiluted raw piggery wastewater, using three microalgal species adapted to high ammonia.

A high ammonia concentration and chemical oxygen demand (COD) in piggery wastewater force it to be diluted before conventional microalgal treatment to reduce ammonia toxicity. Incomplete treatment of ammonia and COD in piggery wastewater may cause eutrophication, resulting in algal blooms. This study tried to treat raw piggery wastewater without dilution, using three strains of microalgae (Chlorella sorokiniana, Coelastrella sp. and Acutodesmus nygaardii) that outcompeted other algae under heterotrophic, mixotrophic, and autotrophic conditions, respectively, through adaptive evolution at high ammonia concentration. The three stepwise processes were designed to remove (1) small particles, COD, and phosphorus in the 1st heterotrophic C. sorokiniana cultivation, (2) ammonia and COD in the 2nd mixotrophic Coelastrella sp. cultivation, and (3) the remaining ammonia in the 3rd photoautotrophic A. nygaardii cultivation. To enhance ammonia uptake rate, each algal species were inoculated after 2-day nitrogen starvation. When the N-starved three species were inoculated at each step sequentially at 7 g/L for 2 days, the final phosphorus, COD, and ammonia removal efficiencies were 100% (16.4-0 mg/L), 92% (6820-545 mg/L), 90% (850-81 mg/L) and turbidity (99%) after total 6 days.

Enhanced and Balanced Microalgal Wastewater Treatment (COD, N, and P) by Interval Inoculation of Activated Sludge.

Although chemical oxygen demand (COD) is an important issue for wastewater treatment, COD reduction with microalgae has been less studied compared to nitrogen or phosphorus removal. COD removal is not efficient in conventional wastewater treatment using microalgae, because the algae release organic compounds, thereby finally increasing the COD level. This study focused on enhancing COD removal and meeting the effluent standard for discharge by optimizing sludge inoculation timing, which was an important factor in forming a desirable algae/bacteria consortium for more efficient COD removal and higher biomass productivity. Activated sludge has been added to reduce COD in many studies, but its inoculation was done at the start of cultivation. However, when the sludge was added after 3 days of cultivation, at which point the COD concentration started to increase again, the algal growth and biomass productivity were higher than those of the initial sludge inoculation and control (without sludge). Algal and bacterial cell numbers measured by qPCR were also higher with sludge inoculation at 3 days later. In a semi-continuous cultivation system, a hydraulic retention time of 5 days with sludge inoculation resulted in the highest biomass productivity and N/P removal. This study achieved a further improved COD removal than the conventional microalgal wastewater treatment, by introducing bacteria in activated sludge at optimized timing.

Optimal strategies for bioremediation of nitrate-contaminated groundwater and microalgae biomass production.

Optimizing the mono-cultivation and mixed cultivation of Chlamydomonas reinhardtii, Chlorella vulgaris, and an Ettlia sp. was evaluated for treating nitrate-contaminated groundwater and biomass production. Ettlia sp. showed the highest nutrient assimilation and growth rate among the three microalgae during bioremediation. Light-dark cycle was the effective condition for nutrient removal and COD mitigation by microalgae. Mixed microalgae with a larger presence of the Ettlia sp. exhibited the highest biomass productivity, nitrate-nitrogen, and phosphate-phosphorus removal rates of 0.21 g/L/d, 16.6, and 3.06 mg/L/d, respectively. An N:P mass ratio of 5 was necessary to increase the mixed-microalgal performance. The settling efficiency of the mixed microalgae increased up to 0.55 when using pH modulation during 30 min. Therefore, applying an Ettlia sp.-dominant consortium was the optimum strategy for the bioremediation of nitrate-contaminated groundwater in 3 days.

Phosphorus optimization for simultaneous nitrate-contaminated groundwater treatment and algae biomass production using Ettlia sp.

The effects of phosphorus concentration on the cell growth, nutrient assimilation, photosynthetic parameters, and biomass recovery of Ettlia sp. were evaluated with batch experiments using groundwater, 50mg/L of N-NO3-, and different concentrations of P-PO43-: 0.5, 2.5, 5, and 10mg/L. The maximum biomass productivity and phosphorus removal rate were 0.2g/L/d and 5.95mg/L/d, respectively, with the highest phosphorus concentration of 10mg/L. However, a phosphorus concentration of 5mg/L (N:P=10) was sufficient to ensure an effective nitrogen removal rate of 11mg/L/d, maximum growth rate of 0.88/d, and biomass recovery of 0.72. The appropriate hydraulic retention time was considered as 4days on a large scale to meet the effluent limitation demands of water. While nitrogen depletion had a significant effect on the photosynthetic parameters and ratio of chlorophyll a to dry cell weight during the stationary phase, the effect of phosphorus was negligible during the cultivation.

Floating rice-culture system for nutrient remediation and feed production in a eutrophic lake.

The increased inputs of nutrients have been demonstrated to be a major contributing factor to the eutrophication of lakes and reservoirs which can lead to the production of harmful algal/cyanobacterial blooms and deleteriously affect the aesthetics of water-bodies. Floating plant-culture systems have been widely used for the ecological remediation of eutrophic water in a cost-effective manner. We investigated the applicability of Korean japonica rice variety 'Nampyeong' in a floating-culture system in a eutrophic lake for nutrient uptake and biomass production. Chemical and organic compound compositions were analyzed two times during the growth stages of the rice plant: 98 DAT (days after transplanting) and 165 DAT. Total nitrogen and phosphorus contributed around 1.36 and 0.15 (% dry weight), respectively, in rice plant components at 165 DAT. Crude protein, lipids, fiber and ash were 4.35, 1.91, 23.66 and 5.55 (% dry weight), respectively. In addition, microcystin levels in the rice plant components ranged from 0.0008 to 0.002 µg/g and did not exceed the recommended tolerable limits. These results suggested that the developed floating rice-culture system showed a good potential as a holistic management approach in terms of nutrient reduction, rice production for further use as feed and for bloom control.

Abundant iron and sulfur oxidizers in the stratified sediment of a eutrophic freshwater reservoir with annual cyanobacterial blooms.

The microbial community in eutrophic freshwater sediment was investigated from a 67-cm-deep sediment core collected from the Daechung Reservoir in South Korea, where cyanobacterial blooms have occurred annually for the past 30 years. The majority of core sediments were characterized by dark-grayish, fine-grained mud with abundant gas-escaped and thinly laminated layers. Intervals of summer and winter seasons were represented by periodic peaks of geochemical profiles of parameters such as grain size and relative carbon mass ratios to various nutrients such as nitrogen, sulfur, and phosphorus. In bacteria, Proteobacteria (66.6%) was the most prevalent phylum, followed by Chloroflexi (8.9%), Bacteroidetes (5.1%), and Spirochaetes (2.6%). Archaea were also abundant, representing approximately half of the total prokaryotes in the sediments. Notably, three Bacteria (Sulfuricurvum, Sideroxydans, and Gallionella) and one Archaea (Thermoplasmata) accounted for 43.4% and 38.4% of the total bacteria and archaea, respectively, implying that iron and sulfur oxidizing microorganisms dominate in this eutrophic freshwater sediment. These results indicate that 1) eutrophic freshwater lakes in monsoon climates undergo a stratified sedimentary process with seasonal and annual variations in geochemical and microbial profiles, and 2) the microbial oxidative metabolism of iron and sulfur is notably active in sediments from a eutrophic lake.

Microcystin Biosynthesis and mcyA Expression in Geographically Distinct Microcystis Strains under Different Nitrogen, Phosphorus, and Boron Regimes.

Roles of nutrients and other environmental variables in development of cyanobacterial bloom and its toxicity are complex and not well understood. We have monitored the photoautotrophic growth, total microcystin concentration, and microcystins synthetase gene (mcyA) expression in lab-grown strains of Microcystis NIES 843 (reference strain), KW (Wangsong Reservoir, South Korea), and Durgakund (Varanasi, India) under different nutrient regimes (nitrogen, phosphorus, and boron). Higher level of nitrogen and boron resulted in increased growth (avg. 5 and 6.5 Chl a mg/L, resp.), total microcystin concentrations (avg. 1.185 and 7.153 mg/L, resp.), and mcyA transcript but its expression was not directly correlated with total microcystin concentrations in the target strains. Interestingly, Durgakund strain had much lower microcystin content and lacked microcystin-YR variant over NIES 843 and KW. It is inferred that microcystin concentration and its variants are strain specific. We have also examined the heterotrophic bacteria associated with cyanobacterial bloom in Durgakund Pond and Wangsong Reservoir which were found to be enriched in Alpha-, Beta-, and Gammaproteobacteria and that could influence the bloom dynamics.

Two-phase photoperiodic cultivation of algal-bacterial consortia for high biomass production and efficient nutrient removal from municipal wastewater.

This study investigated the photoperiodic effects on the biomass production and nutrient removal in the algal-bacterial wastewater treatment, under the following three conditions: (1) a natural 12h:12h LD cycle, (2) a dark-elongated 12h:60h LD cycle, and (3) a two-phase photoperiodic 12h:60h LD, followed by 12h:12h LD cycles. The two-phase photoperiodic operation showed the highest dry cell weight and lipid productivity (282.6mgL(-1)day(-1), 71.4mgL(-1)day(-1)) and most efficient nutrient removals (92.3% COD, 95.8% TN, 98.1% TP). The genetic markers and sequencing analyses indicated rapid increments of bacteria, subsequent growths of Scenedesmus, and stabilized population balances between algae and bacteria. In addition, the two-phase photoperiod provided a higher potential for the algal-bacterial consortia to utilize various organic carbon substrates.

Effects of photoperiod on nutrient removal, biomass production, and algal-bacterial population dynamics in lab-scale photobioreactors treating municipal wastewater.

Effects of photoperiod were investigated in lab-scale photobioreactors containing algal-bacterial consortia to reduce organic nutrients from municipal wastewater. Under three photoperiod conditions (12 h:12 h, 36 h:12 h, and 60 h:12 h dark­light cycles), nutrient removals and biomass productions were measured along with monitoring microbial population dynamics. After a batch operation for 12 days, 59­80% carbon, 35­88% nitrogen, and 43­89% phosphorus were removed from influents, respectively. In this study, carbon removal was related positively to the length of dark cycles, while nitrogen and phosphorus removals inversely. On the contrast, the highest microbial biomass in terms of chlorophyll a, dry cell weight, and algal/bacterial rRNA gene markers was produced under the 12 h:12 h dark­light cycle among the three photoperiods. The results showed 1) simultaneous growths between algae and bacteria in the microbial consortia and 2) efficient nitrogen and phosphorus removals along with high microbial biomass production under prolonged light conditions. Statistical analyses indicated that carbon removal was significantly related to the ratio of bacteria to algae in the microbial consortia along with prolonged dark conditions (p < 0.05). In addition, the ratio of nitrogen removal to phosphorus removal decreased significantly under prolonged dark conditions (p < 0.001). These results indicated that the photoperiod condition has remarkable impacts on adjusting nutrient removal, producing microbial biomass, and altering algal-bacterial population dynamics. Therefore, the control of photoperiod was suggested as an important operating parameter in the algal wastewater treatment.

Increased microalgae growth and nutrient removal using balanced N:P ratio in wastewater.

Microalgal cultivation using wastewater is now regarded as essential for biodiesel production, as two goals can be achieved simultaneously; that is, nutrient removal efficiency and biomass production. Therefore, this study examined the effects of carbon sources, the N:P ratio, and the hydraulic retention time (HRT) to identify the optimal conditions for nutrient removal efficiency and biomass production. The effluent from a 2nd lagoon was used to cultivate microalgae. Whereas the algal species diversity and lipid content increased with a longer HRT, the algal biomass productivity decreased. Different carbon sources also affected the algal species composition. Diatoms were dominant with an increased pH when bicarbonate was supplied. However, 2% CO(2) gas led to a lower pH and the dominance of filamentous green algae with a much lower biomass productivity. Among the experiments, the highest chlorophyll-a concentration and lipid productivity were obtained with the addition of phosphate up to 0.5 mg/l P, since phosphorus was in short supply compared with nitrogen. The N and P removal efficiencies were also higher with a balanced N:P ratio, based on the addition of phosphate. Thus, optimizing the N:P ratio for the dominant algae could be critical in attaining higher algal growth, lipid productivity, and nutrient removal efficiency.

Multi-level stressor analysis from the DNA/biochemical level to community levels in an urban stream and integrative health response (IHR) assessments.

The objectives of this study were to identify multi-level stressors at the DNA/biochemical level to the community level in fish in an urban stream and to develop an integrative health response (IHR) model for ecological health diagnosis. A pristine control site (S (c) ) and an impacted site (S (i) ) were selected from among seven pre-screened sites studied over seven years. Various chemical analyses indicated that nutrient enrichment (Nitrogen, Phosphorus) and organic pollution were significantly greater (t > 8.783, p < 0.01) at the S (i) site compared to the S (c) site. Single-cell gel electrophoresis (comet assays) of DNA-level impairment indicated significantly (t = 5.678, p < 0.01) greater tail intensity, expressed as % tail-DNA, at the S (i) site and genotoxic responses were detected in the downstream reach. Ethoxyresorufin-O-deethylase (EROD) assays, as a physiological bioindicator, were 2.8-fold higher (p < 0.05, NK-test after ANOVA) at the S (i) site. Tissue analysis using a necropsy-based health assessment index (NHAI) showed distinct internal organ disorders in three tissues, i.e., liver, kidney, and gill, at the S (i) site. Population-level analysis using the sentinel species Zacco platypus showed that the regression coefficient (b) was 3.012 for the S (i) site and 2.915 for the S (c) site, indicating population skewness in the downstream reach. Community-level health was impaired at the S (i) site based on an index of biological integrity (IBI), and physical habitat modifications were identified by a qualitative habitat evaluation index (QHEI). Overall, the model values for the integrative health response (IHR), developed using the star plot approach, were 3.22 (80.5%) at the S (c) site and 0.74 (18.5%) at the S (i) site, indicating that, overall, ecological health impairments were evident in the urban reach. Our study was based on multi-level approaches using biological organization and the results suggest that there is a pivotal point of linkage between mechanistic understanding and real ecological consequences of environmental stressors.

Dynamics of microcystin production and quantification of potentially toxigenic Microcystis sp. using real-time PCR.

Cyanobacterial blooms in eutrophied water body are generally composed of various genotypes with or without microcystin-producing genes (mcy gene cluster). Thus there is a need for quantification of potent toxin producing strains. The present study aimed at identifying microcystin variants and its producer strains in Durgakund pond, Varanasi, India, based on quantification of cpcBA-IGS and mcyA (condensation domain) genes using real-time PCR and LC-MS. Increase in microcystin concentrations was correlated with increase in mcyA copy number and the level of pigments (chlorophyll a, phycocyanin and carotenoids). Also, selected environmental factors (water temperature, light irradiance, rainfall, pH, N and P) and the concentration of microcystin variants (MC-LR, -RR and -YR) were also assessed in samples during May 2010 to April 2011 to establish the possible correlation among these parameters. Nutrients favored cyanobacterial bloom but it could not be correlated with the levels of microcystin variants and seemed to be geographically specific. Microcystis sp. dominant in the pond comprised potentially toxigenic cells. The ratio of potentially toxigenic Microcystis sp. to that of total Microcystis sp. ranged from 0% to 14%. Such studies paved the way to identify and quantify the most potent microcystin producer in the tropical aquatic body.

Lysobacter panaciterrae sp. nov., isolated from soil of a ginseng field.

A Gram-negative, aerobic, rod-shaped, non-spore-forming bacterial strain, designated Gsoil 068(T), was isolated from soil of a ginseng field in Pocheon Province (South Korea), and was characterized to determine its taxonomic position by using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain Gsoil 068(T) belonged to the family Xanthomonadaceae, class Gammaproteobacteria, and was related most closely to Lysobacter brunescens ATCC 29482(T) and Lysobacter gummosus ATCC 29489(T) (96.1 % sequence similarity). The G+C content of the genomic DNA of strain Gsoil 068(T) was 67.0 mol%. The detection of a quinone system with ubiquinone Q-8 as the predominant component and a fatty acid profile with iso-C(15 : 0), iso-C(17 : 1)omega9c, iso-C(17 : 0) and iso-C(11 : 0) 3-OH as the major components supported the affiliation of strain Gsoil 068(T) to the genus Lysobacter. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 068(T) is considered to represent a novel species of the genus Lysobacter, for which the name Lysobacter panaciterrae sp. nov. is proposed. The type strain is Gsoil 068(T) (=KCTC 12601(T) =DSM 17927(T)).

Monitoring bacterial population dynamics using real-time PCR during the bioremediation of crude-oil-contaminated soil.

We evaluated the activity and abundance of the crude oil- degrading bacterium Nocardia sp. H17-1 during bioremediation of oil-contaminated soil, using real-time PCR. The total petroleum hydrocarbon (TPH) degradation rate constants (k) of the soils treated with and without H17-1 were 0.103 d-1 and 0.028 d-1, respectively. The degradation rate constant was 3.6 times higher in the soil with H17-1 than in the soil without H17-1. In order to detect and quantify the Nocardia sp. H17-1 in soil samples, we quantified the genes encoding 16S ribosomal RNA (16S rRNA), alkane monooxygenase (alkB4), and catechol 2,3-dioxygenase (23CAT) with real-time PCR using SYBR green. The amounts of H17-1 16S rRNA and alkB4 detected increased rapidly up to 1,000-folds for the first 10 days, and then continued to increase only slightly or leveled off. However, the abundance of the 23CAT gene detected in H17-1-treated soil, where H17-1 had neither the 23CAT gene for the degradation of aromatic hydrocarbons nor the catechol 2,3-dioxygenase activity, did not differ significantly from that of the untreated soil (alpha=0.05, p>0.22). These results indicated that H17-1 is a potential candidate for the bioaugmentation of alkane-contaminated soil. Overall, we evaluated the abundance and metabolic activity of the bioremediation strain H17-1 using real-time PCR, independent of cultivation.

Raceway cultivation of Spirulina platensis using underground water.

The semi-outdoor cultivation of Spirulina platensis was attempted using an underground-water-based medium. Occurrence of contaminant organisms such as Chlorella sp. and Chlamydomonas sp. was not found from a microscopic observation and bacteria were not detected from denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified 16S rDNA during the cultivation, owing to pH control and the high quality of the underground water. The mean productivity was high at 10.5 g/m2/d with a range of 4.2-12.3 g/m2/d despite the unfavorable weather conditions of the rainy season. The cultivated S. platensis included a normal protein content of 58.9%. Consequently, the underground water improved the biomass productivity and the biomass quality because of an abundant supplementation of natural minerals and through a contaminant-free culture.

Monitoring of microbial diversity and activity during bioremediation of crude oil-contaminated soil with different treatments.

The present study compared the microbial diversity and activity during the application of various bioremediation processes to crude oil-contaminated soil. Five different treatments, including natural attenuation (NA), biostimulation (BS), biosurfactant addition (BE), bioaugmentation (BA), and a combined treatment (CT) of biostimulation, biosurfactant addition, and bioaugmentation, were used to analyze the degradation rate and microbial communities. After 120 days, the level of remaining hydrocarbons after all the treatments was similar, however, the highest rate (k) of total petroleum hydrocarbon (TPH) degradatioN was observed with the CT treatment (P < 0.05). The total bacterial counts increased during the first 2 weeks with all the treatments, and then remained stable. The bacterial communities and alkane monooxygenase gene fragment, alkB, were compared by denaturing gradient gel electrophoresis (DGGE). The DGGE analyses of the BA and CT treatments, which included Nocardia sp. H17-1, revealed a simple dominant population structure, compared with the other treatments. The Shannon-Weaver diversity index (H') and Simpson dominance index (D), calculated from the DGGE profiles using 16S rDNA, showed considerable qualitative differences in the community structure before and after the bioremediation treatment as well as between treatment conditions.

Bacillus pocheonensis sp. nov., a moderately halotolerant, aerobic bacterium isolated from soil of a ginseng field.

A Gram-positive, non-motile, endospore-forming bacterial strain, designated Gsoil 420T, was isolated from soil of a ginseng field in Pocheon Province, South Korea, and was characterized, using a polyphasic approach, in order to determine its taxonomic position. The novel isolate consisted of strictly aerobic, rod-shaped cells and was able to grow in medium supplemented with up to 12% NaCl at 25 degrees C and pH 6.5-7.0. Comparative 16S rRNA gene sequence analysis showed that strain Gsoil 420T fell within the radiation of the cluster comprising Bacillus species and formed a coherent cluster with Bacillus niacini (16S rRNA gene sequence similarity, 98.6%), Bacillus bataviensis (98.6%), Bacillus soli (98.3%), Bacillus drentensis (98.0%), Bacillus novalis (98.0%), Bacillus vireti (97.9%), Bacillus foraminis (97.6%), Bacillus fumarioli (97.4%) and Bacillus jeotgali (97.0%). The levels of 16S rRNA gene sequence similarity with respect to other Bacillus species with validly published names were less than 96.8%. Strain Gsoil 420T had a genomic DNA G+C content of 44.9 mol% and the predominant respiratory quinone was MK-7. The major fatty acids were anteiso-C15:0 (33.9%), iso-C15:0 (24.5%) and iso-C14:0 (19.9%). These chemotaxonomic results supported the affiliation of strain Gsoil 420T to the genus Bacillus. However, low DNA-DNA relatedness values and distinguishing phenotypic characteristics allowed genotypic and phenotypic differentiation of strain Gsoil 420T from recognized Bacillus species. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain Gsoil 420T represents a novel species of the genus Bacillus, for which the name Bacillus pocheonensis sp. nov. is proposed. The type strain is Gsoil 420T (=KCTC 13943T=DSM 18135T).

Brevibacillus ginsengisoli sp. nov., a denitrifying bacterium isolated from soil of a ginseng field.

A Gram-positive, rod-shaped, spore-forming bacterium, Gsoil 3088T, was isolated from soil from a ginseng field in Pocheon Province in South Korea and characterized in order to determine its taxonomic position. On the basis of 16S rRNA gene sequence similarity, strain Gsoil 3088T was shown to belong to the family Paenibacillaceae, being related to Brevibacillus centrosporus (96.6%), Brevibacillus borstelensis (96.3%), Brevibacillus parabrevis (96.1%), Brevibacillus formosus (96.1%), Brevibacillus brevis (96.1%) and Brevibacillus laterosporus (96.0%). The phylogenetic distances from other validly described species within the genus Brevibacillus were greater than 4.0% (i.e. there was less than 96.0% similarity). The G+C content of the genomic DNA was 52.1 mol%. Phenotypic and chemotaxonomic data (major menaquinone, MK-7; fatty acid profile, iso-C15:0, iso-C14:0 and anteiso-C15:0) supported the affiliation of strain Gsoil 3088T to the genus Brevibacillus. The results of physiological and biochemical tests allowed strain Gsoil 3088T to be distinguished genotypically and phenotypically from Brevibacillus species with validly published names. Strain Gsoil 3088T, therefore, represents a novel species of the genus Brevibacillus, for which the name Brevibacillus ginsengisoli sp. nov. is proposed. The type strain is Gsoil 3088T (=KCTC 13938T=LMG 23403T).

Effects of crude oil, oil components, and bioremediation on plant growth.

The phytotoxic effects of crude oil and oil components on the growth of red beans (Phaseolus nipponesis OWH1) and corn (Zea mays) was investigated. In addition, the beneficial effects of bioremediation with the oil-degrading microorganism, Nocardia sp. H17-1, on corn and red bean growth in oil-contaminated soil was also determined. It was found that crude oil-contaminated soil (10,000mg/kg) was phytotoxic to corn and red beans. In contrast, obvious phytotoxicity was not observed in soils contaminated with 0-1000 mg/kg of aliphatic hydrocarbons such as decane (C10) and eicosane (C20). Phytotoxicity was observed in soils contaminated with 10-1000mg/kg of the poly aromatic hydrocarbons (PAHs) naphthalene, phenanthrene, and pyrene. It was observed that phytotoxicity increased with the number of aromatic rings, and that corn was more sensitive than red beans to PAH-contaminated soil. Bioremediation with Nocardia sp. H17-1 reduced phytotoxicity more in corn than in red bean, suggesting that this microbial species might degrade PAHs to some degree.