Aerobic versus Anaerobic Microbial Degradation of Etofenprox in a California rice field soil

The microbial degradation of etofenprox, an ether pyrethroid, was characterized under anaerobic (flooded) and aerobic (nonflooded) California rice field soil conditions by determination of its half-life (t1/2) and dissipation rate constant (k) and identification and quantification of degradation products at both 22 and 40 °C using LC-MS/MS. The overall anaerobic t1/2 at 22 °C ranged from 49.1 to 100 days (k=-0.0141 to -0.0069 days(-1)) compared to 27.0 days (k=-0.0257 days(-1)) at 40 °C, whereas under aerobic conditions the overall t1/2 was 27.5 days (k=-0.0252 days(-1)) at 22 °C compared to 10.1-26.5 days (k=-0.0686 to -0.0262 days(-1)) at 40 °C. The biphasic dissipation profiles were also fit to a first-order model to determine the t1/2 and k for both the fast and slow kinetic regions of the dissipation curves. Hydroxylation at the 4'-position of the phenoxy phenyl ring was the major metabolic process under anaerobic conditions for both 22 °C (maximum% yield of applied etofenprox mass=1.3±0.7%) and 40 °C (max % yield=1.2±0.8%). Oxidation of the ether moiety to the ester was the major metabolite under aerobic conditions at 22 °C (max% yield=0.5±0.1%), but at 40 °C increased amounts of the hydroxylated form were produced (max% yield=0.7±0.2%, compared to 0.3±0.1% for the ester). The hydrolytic product of the ester, 3-phenoxybenzoic acid (3-PBA), was not detected in any samples. Sterilized control soils showed little etofenprox degradation over the 56-day incubation period. Thus, the microbial population in a flooded soil was able to transform and contribute to the overall dissipation of etofenprox. The simulated summer temperature extreme (40 °C) increased the overall degradation.     

Allergenicity assessment of the papaya ringspot virus coat protein expressed in transgenic rainbow papaya

The virus-resistant, transgenic commercial papaya Rainbow and SunUp (Carica papaya L.) have been consumed locally in Hawaii and elsewhere in the mainland United States and Canada since their release to planters in Hawaii in 1998. These papaya are derived from transgenic papaya line 55-1 and carry the coat protein (CP) gene of papaya ringspot virus (PRSV). The PRSV CP was evaluated for potential allergenicity, an important component in assessing the safety of food derived from transgenic plants. The transgene PRSV CP sequence of Rainbow papaya did not exhibit greater than 35% amino acid sequence homology to known allergens, nor did it have a stretch of eight amino acids found in known allergens which are known common bioinformatic methods used for assessing similarity to allergen proteins. PRSV CP was also tested for stability in simulated gastric fluid and simulated intestinal fluid and under various heat treatments. The results showed that PRSV CP was degraded under conditions for which allergenic proteins relative to nonallergens are purported to be stable. The potential human intake of transgene-derived PRSV CP was assessed by measuring CP levels in Rainbow and SunUp along with estimating the fruit consumption rates and was compared to potential intake estimates of PRSV CP from naturally infected nontransgenic papaya. Following accepted allergenicity assessment criteria, our results show that the transgene-derived PRSV CP does not pose a risk of food allergy.     

FUM13 encodes a short chain dehydrogenase/reductase required for C-3 carbonyl reduction during fumonisin biosynthesis in Gibberella moniliformis

Fumonisins are polyketide-derived mycotoxins produced by the filamentous fungus Gibberella moniliformis (anamorph Fusarium verticillioides). Wild-type strains of the fungus produce predominantly four B-series fumonisins, designated FB(1), FB(2), FB(3), and FB(4). Recently, a cluster of 15 putative fumonisin biosynthetic genes (FUM) was described in G. moniliformis. We have now conducted a functional analysis of FUM13, a gene in the cluster that is predicted by amino acid sequence similarity to encode a short chain dehydrogenase/reductase (SDR). Mass spectrometric analysis of metabolites from FUM13 deletion mutants revealed that they produce approximately 10% of wild-type levels of B-series fumonisins as well as two previously uncharacterized compounds. NMR analysis revealed that the new compounds are similar in structure to FB(3) and FB(4) but that they have a carbonyl function rather than a hydroxyl function at carbon atom 3 (C-3). These results indicate that the FUM13 protein catalyzes the reduction of the C-3 carbonyl to a hydroxyl group and are the first biochemical evidence directly linking a FUM gene to a specific reaction during fumonisin biosynthesis. The production of low levels of FB(1), FB(2), FB(3), and FB(4), which have a C-3 hydroxyl, by the FUM13 mutants suggests that G. moniliformis has an additional C-3 carbonyl reductase activity but that this enzyme functions less efficiently than the FUM13 protein.     

Procyanidin and catechin contents and antioxidant capacity of cocoa and chocolate products

Cocoa and chocolate products from major brands were analyzed blind for total antioxidant capacity (AOC) (lipophilic and hydrophilic ORAC(FL)), catechins, and procyanidins (monomer through polymers). Accuracy of analyses was ascertained by comparing analyses on a NIST standard reference chocolate with NIST certified values. Procyanidin (PC) content was related to the nonfat cocoa solid (NFCS) content. The natural cocoa powders (average 87% of NFCS) contained the highest levels of AOC (826 +/- 103 micromol of TE/g) and PCs (40.8 +/- 8.3 mg/g). Alkalized cocoa (Dutched powders, average 80% NFCS) contained lower AOC (402 +/- 6 micromol of TE /g) and PCs (8.9 +/- 2.7 mg/g). Unsweetened chocolates or chocolate liquor (50% NFCS) contained 496 +/- 40 micromol of TE /g of AOC and 22.3 +/- 2.9 mg/g of PCs. Milk chocolates, which contain the least amount of NFCS (7.1%), had the lowest concentrations of AOC (80 +/- 10 micromol of TE /g) and PCs (2.7 +/- 0.5 mg/g). One serving of cocoa (5 g) or chocolate (15 or 40 g, depending upon the type of chocolate) provides 2000-9100 micromol of TE of AOC and 45-517 mg of PCs, amounts that exceed the amount in a serving of the majority of foods consumed in America. The monomers through trimers, which are thought to be directly bioavailable, contributed 30% of the total PCs in chocolates. Hydrophilic antioxidant capacity contributed >90% of AOC in all products. The correlation coefficient between AOC and PCs in chocolates was 0.92, suggesting that PCs are the dominant antioxidants in cocoa and chocolates. These results indicate that NFCS is correlated with AOC and PC in cocoa and chocolate products. Alkalizing dramatically decreased both the procyanidin content and antioxidant capacity, although not to the same extent.     

Concentrations of anthocyanins in common foods in the United States and estimation of normal consumption

Anthocyanins (ACNs) are water-soluble plant pigments that have important functions in plant physiology as well as possible health effects. Over 100 common foods were screened for ACNs, and 24 of them were found to contain ACNs. Concentrations of total ACNs varied considerably from 0.7 to 1480 mg/100 g of fresh weight in gooseberry ('Careless' variety) and chokeberry, respectively. Not only does the concentration vary, but the specific anthocyanins present in foods are also quite different. Only six common aglycones, delphinidin, cyanidin, petunidin, pelargonidin, peonidin, and malvidin, were found in all of these foods. However, their sugar moieties and acylation patterns varied from food to food. Results from this study will add to the available data for the USDA Nutrient Database of flavonoids. On the basis of the concentration data and updated food intake data from NHANES 2001-2002, the daily intake of ACNs is estimated to be 12.5 mg/day/person in the United States. Of the different aglycones, cyanidin, delphinidin, and malvidin were estimated to contribute 45, 21, and 15%, respectively, of the total ACN intake. Nonacylated contributed 77% compared to 23% from acylated ACNs.     

Microbial degradation of penoxsulam in flooded rice field soils

The degradation of penoxsulam [2-(2,2-difluoroethoxy)-N-5,8-dimethoxy[1,2,4]triazolo[1,5-C]pyrimidin-2-yl-6-(trifluoromethyl)benzene-sulfonamide] was studied in flasks simulating flooded rice field conditions using four representative rice field soils from the Sacramento Valley. Degradation half-lives (t(1/2) values) ranged between 2 and 13 days. Increased degradation rates were observed in flask systems with steeper redox gradients between the flooded soil layer and the overlaying water. Two transient metabolites were identified that were temporarily formed in amounts exceeding 5% of the total initial mass of penoxsulam. The results of high-performance liquid chromatography/(14)C radiodetection studies indicate that the degradation of the triazolopyrimidine system and its substituents is the main pathway of microbial transformation processes. Microbial activity, as measured by dehydrogenase activity, was not affected by penoxsulam concentrations corresponding to the proposed maximum annual use rate of 40 g active ingredient/ha.     

Cross-modality of texture and aroma perception is independent of orthonasal or retronasal stimulation

To assess the influence of orthonasal and retronasal stimulation on cross-modal interactions between texture and flavor perception of food, a series of experiments have been conducted. Healthy human subjects were exposed to strawberry aroma pulses delivered by a computer-controlled stimulator based on air dilution olfactometry. Just prior to exposure to the aroma, the human subjects consumed water, custard, or protein gels with different textures without any added aroma. The aroma was delivered as a sequence of aroma pulses, in either an orthonasal or a retronasal fashion. The retronasal presentation of aroma with concomitant presentation of texture is thought to more closely mimick the in vivo flavor release of semisolid food products as compared to orthonasal stimulation. The time between oral consumption of the food, including swallowing, and the exposure to the aroma varied between 0.5 and 6.5 s. The subjects rated the intensity of the strawberry aroma. It was observed that the intensity of aroma decreased with increasing firmness of the food that was consumed. Aroma pulses delivered 6.5 s after swallowing were perceived as being more intense as compared to aroma pulses delivered immediately after swallowing. In conjunction with late delivery, the effect cross-modal interactions apparently decreased. Significantly higher odor intensities were reported for the aroma stimuli supplied orthonasally in comparison to retronasal administration. The observed cross-modal effect of texture on aroma intensity was not significantly altered by the mode of aroma delivery, i.e., orthonasal or retronasal stimulus administration.     

Removal of Benzene by the Indoor Plant/Substrate Microcosm and Implications for Air Quality

Water, Air, &; Soil Pollution - The quality of the indoor environment has become a major health consideration, since urban-dwellers spend 80-90% of their time indoors, where air pollution can be...