A Simply Modified Lymphocyte for Systematic Cancer Therapy

Cytotherapy has received considerable attention in the field of cancer therapy, and various chemical or genetic methods have been applied to remold natural cells for improved therapeutic outcome of cytotherapy. A simple method to modify lymphocytes for cancer treatment by using a clinically used molecule, δ-aminolevulinic acid (δ-ALA), is reported here. After incubation with this molecule, tumor-targeted lymphocytes spontaneously synthesize anti-neoplastic drug protoporphyrin X (PpIX), and specifically accumulate in cancer tissue. Under periodic 630 nm laser irradiation, lymphocytes generate vesicle-like apoptotic body (Ab) containing the above-produced PpIX, and the facilitated delivery of PpIX from Ab makes an excellent therapeutic effect for Ras-mutated cancer cells under a second irradiation. Importantly, a microfluidic device is further fabricated to simplify cell sorting and drug synthesis with a one-step operation, which could promote generalization of this strategy. In vitro and in vivo studies confirm the success of such an easy-operated and global-regulated strategy for cancer therapy.

Radiosensitizing Effect of 5-Aminolevulinic Acid and Protoporphyrin IX on Carbon-ion Beam Irradiation

BACKGROUND/AIM

Carbon-ion beam is one of the most advanced radiations used for cancer treatment. However, there are tumors that are difficult to suppress with carbon-ion beam alone, thus necessitating development of drugs that can enhance its therapeutic effect. In this regard, the radiosensitizing effect of 5-aminolevulinic acid (ALA) and protoporphyrin IX (PpIX), that is a metabolic intermediate of ALA, on carbon-ion beam was investigated.

MATERIALS AND METHODS

Radiosensitizing activity, mitochondrial ROS and DNA double-strand break production of ALA and PpIX were evaluated by irradiation with 1.0 or 1.5-Gy carbon-ion beam to mouse mammary EMT6 tumor cells.

RESULTS

Combination of carbon-ion beam and ALA or PpIX showed a significant enhancement of its cytotoxic activity through a significant increase in ROS production in mitochondria. Furthermore, the combined activity of carbon-ion beam and ALA resulted in a significant increase in DNA double-strand breakage.

CONCLUSION

ALA selectively accumulates in the mitochondria and PpIX synthesized from ALA reacts with carbon-ion beam to produce ROS that exert antitumor activity.

Red-light excitation of protoporphyrin IX fluorescence for subsurface tumor detection

OBJECTIVE The objective of this study was to detect 5-aminolevulinic acid (ALA)-induced tumor fluorescence from glioma below the surface of the surgical field by using red-light illumination. METHODS To overcome the shallow tissue penetration of blue light, which maximally excites the ALA-induced fluorophore protoporphyrin IX (PpIX) but is also strongly absorbed by hemoglobin and oxyhemoglobin, a system was developed to illuminate the surgical field with red light (620-640 nm) matching a secondary, smaller absorption peak of PpIX and detecting the fluorescence emission through a 650-nm longpass filter. This wide-field spectroscopic imaging system was used in conjunction with conventional blue-light fluorescence for comparison in 29 patients undergoing craniotomy for resection of high-grade glioma, low-grade glioma, meningioma, or metastasis. RESULTS Although, as expected, red-light excitation is less sensitive to PpIX in exposed tumor, it did reveal tumor at a depth up to 5 mm below the resection bed in 22 of 24 patients who also exhibited PpIX fluorescence under blue-light excitation during the course of surgery. CONCLUSIONS Red-light excitation of tumor-associated PpIX fluorescence below the surface of the surgical field can be achieved intraoperatively and enables detection of subsurface tumor that is not visualized under conventional blue-light excitation. Clinical trial registration no.: NCT02191488 (clinicaltrials.gov).

Spectral Radiance of Protoporphyrin IX Fluorescence and Its Histopathological Implications in 5-Aminolevulinic Acid-Guided Surgery for Glioblastoma

OBJECTIVE

This study is intended to objectively clarify the relationship between the fluorescence intensity emitted by protoporphyrin IX (PpIX), which is a metabolite of 5-aminolevulinic acid (ALA), and histological findings during glioblastoma surgery.

BACKGROUND

ALA is widely used for the intraoperative detection of tumors. There are several reports about the fluorescence of PpIX and the histological findings of tumors, but judgments about the fluorescence intensity depend largely on the subjective sense of each surgeon.

METHODS

We quantified the PpIX fluorescence intensity emitted from tissue specimens using a spectroradiometer and evaluated the relationship between a spectral radiance of 635 nm and the histopathological features of surgical specimens of glioblastoma. Surgical samples from glioblastoma patients consist of a strongly fluorescent area (SFA) or vaguely fluorescent area (VFA). Hematoxylin and eosin staining, immunohistochemical Ki-67, and CD31 staining were performed to evaluate the cell density, MIB-1 index, and vascularity, respectively. The fluorescence intensities of each sample were compared with each histopathological parameter.

RESULTS

Cell density, MIB-1 index, and total vascular area were significantly correlated with PpIX fluorescence radiance. 87.5% of SFA were judged to be tumor bulk consisting mostly of tumor cells and 12.5% peritumoral invaded brain. In the VFA, 100% of specimens were judged to be peritumoral invaded brain.

CONCLUSIONS

ALA-induced PpIX fluorescence has quantitatively correlated well with histopathological malignant features both in SFA and VFA. These findings suggest that not only SFA but also VFA should be removed to the highest extent that does not cause neurological symptoms.

Neurosurgical microscopic solid laser-based light inhibits photobleaching during fluorescence-guided brain tumor removal with 5-aminolevulinic acid

BACKGROUND

Fluorescence image guided surgery (FIGS) with 5-aminolevulinic acid for malignant gliomas improves surgical outcome. One of the problems during FIGS is photobleaching under surgical microscopic white light. A solid laser-based white light source for neurosurgery that we developed does not include light with a wavelength of around 405nm, which is strongly absorbed by protoporphyrin IX. In the present study, we examined the efficacy of this light source to prevent the photobleaching of protoporphyrin IX-induced fluorescence.

METHODS

Filter papers transfused with protoporphyrin IX solution and a coronally sectioned F98 glioma rat model pretreated with 50mg/kg 5-aminolevulinic acid were continuously exposed to white light. One group was exposed to conventional xenon-based white light and another group was exposed to laser-based white light. Fluorescence at a wavelength of 635nm was measured with a radiospectrometer (in vitro study) and the relative fluorescence brightness was also measured in digital images (in vivo study) under excitation from violet blue light emitted from diodes every 5min.

RESULTS AND CONCLUSION

Estimated time for 50% photobleaching was prolonged about two times in the laser-based white light exposure group compared with that in the xenon-based white light exposure group (9.1/18.7min). In the brain tumor rat model, it was also prolonged about 2.7 times (15.1/40.7min). A laser-based white light source may inhibit photobleaching during FIGS for malignant gliomas. This light source for neurosurgical microscopy has the potential to prolong the prognosis of malignant glioma patients.

5-Aminolevulinic acid-based photodynamic therapy of chordoma: In vitro experiments on a human tumor cell line

BACKGROUND

Chordomas are very rare tumors of the skull base and the sacrum. They show infiltrating and destructive growth and are known to be chemo- and radio-resistant. After surgical resection, the recurrence rate is high and overall survival limited. As current adjuvant treatments are ineffective, new treatment concepts are urgently needed. 5-aminolevulinic acid-based photodynamic therapy (5-ALA based PDT) showed promising results for malignant gliomas. However, it is unknown so far, whether chordomas accumulate protoporphyrin IX (PPIX) after application of 5-ALA and whether they are sensitive to subsequent 5-ALA based PDT.

METHODS

The immortalized human chordoma cells U-CH2 were used as in vitro model. After incubation for 4h or 6h with different 5-ALA concentrations, PPIX accumulation was determined by flow cytometry. To assess sensitivity to PDT, chordoma cells were incubated at 30.000cells/well (high cell density) or 15.000cells/well (low cell density) with graded doses of 5-ALA (0-50μg/ml) in 96-well plates and subsequently exposed to laser light of 635nm wavelength (18.75J/cm2). Cell survival was measured 24h after exposure to laser light using the WST-1 assay.

RESULTS

U-CH2 cells dose-dependently accumulated PPIX (ANOVA; p<0.0001). PPIX fluorescence was significantly higher, when cells were incubated with 5-ALA for 6h compared to 4h at higher 5-ALA concentrations (ANOVA/Bonferroni; p≤0.05 for≥30μg/ml 5-ALA). For both cell densities, a 5-ALA dose-dependent decline in viability was observed (ANOVA; p<0.0001). Viability was significantly lower at higher 5-ALA concentrations, when 30.000 cells/wells were treated compared to 15.000cells/well (ANOVA/Bonferroni; p≤0.001 for≥30μg/ml 5-ALA). LD50 was 30.25μg/ml 5-ALA.

CONCLUSION

The human UCH-2 cell line was a very useful in vitro model to study different effects of 5-ALA based PDT. For the first time, it could be shown that human chordoma cells may be destroyed by 5-ALA/PDT.

5-Aminolevulinic acid modulates antioxidant defense systems and mitigates drought-induced damage in Kentucky bluegrass seedlings

Drought stress occurs frequently and severely as a result of global climate change, and it exerts serious effects on plants. 5-Aminolevulinic acid (5-ALA) plays a crucial role in conferring abiotic stress tolerance in plants. To enhance the drought tolerance of turfgrass and investigate the effects of 5-ALA on antioxidant metabolism and gene expression under drought stress conditions, exogenous 5-ALA was applied by foliar spraying before Kentucky bluegrass (Poa pratensis L.) seedlings were exposed to drought [induced by 10% polyethylene glycol (PEG)] stress for 20 days. 5-ALA pretreatment increased turf quality (TQ) and leaf relative water content (RWC) while reducing reactive oxygen species (ROS) production including H2O2 content and O2•- generation rate, lipoxygenase (LOX) activity, and malondialdehyde (MDA) content under drought stress. 5-ALA pretreatment maintained ascorbate (AsA) and glutathione (GSH) contents and the ASA/DHA and GSH/GSSG ratios at high levels, and it enhanced the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR), which are crucial for scavenging drought-induced ROS. In addition, 5-ALA upregulated the relative expression levels of Cu/ZnSOD, APX, GPX, and DHAR but downregulated those of CAT and GR under drought stress. These results indicated that the application of 5-ALA might improve turfgrass quality and promote drought tolerance in Kentucky bluegrass through reducing oxidative damage and increasing non-enzyme antioxidant levels and antioxidant enzyme activity at transcriptional and posttranscriptional levels.

Neuroprotective effect of 5-aminolevulinic acid against low inorganic phosphate in neuroblastoma SH-SY5Y cells

PiT-1 (encoded by SLC20A1) and PiT-2 (encoded by SLC20A2) are type-III sodium-dependent phosphate cotransporters (NaPiTs). Recently, SLC20A2 mutations have been found in patients with idiopathic basal ganglia calcification (IBGC), and were predicted to bring about an inability to transport Pi from the extracellular environment. Here we investigated the effect of low Pi loading on the human neuroblastoma SH-SY5Y and the human glioblastoma A172 cell lines. The results show a different sensitivity to low Pi loading and differential regulation of type-III NaPiTs in these cells. We also examined whether 5-aminolevulinic acid (5-ALA) inhibited low Pi loading-induced neurotoxicity in SH-SY5Y cells. Concomitant application of 5-ALA with low Pi loading markedly attenuated low Pi-induced cell death and mitochondrial dysfunction via the induction of HO-1 by p38 MAPK. The findings provide us with novel viewpoints to understand the pathophysiology of IBGC, and give a new insight into the clinical prevention and treatment of IBGC.

Enhancement of 5-aminolevulinic acid-based fluorescence detection of side population-defined glioma stem cells by iron chelation

Cancer stem cells (CSCs) are dominantly responsible for tumor progression and chemo/radio-resistance, resulting in tumor recurrence. 5-aminolevulinic acid (ALA) is metabolized to fluorescent protoporphyrin IX (PpIX) specifically in tumor cells, and therefore clinically used as a reagent for photodynamic diagnosis (PDD) and therapy (PDT) of cancers including gliomas. However, it remains to be clarified whether this method could be effective for CSC detection. Here, using flow cytometry-based analysis, we show that side population (SP)-defined C6 glioma CSCs (GSCs) displayed much less 5-ALA-derived PpIX fluorescence than non-GSCs. Among the C6 GSCs, cells with ultralow PpIX fluorescence exhibited dramatically higher tumorigenicity when transplanted into the immune-deficient mouse brain. We further demonstrated that the low PpIX accumulation in the C6 GSCs was enhanced by deferoxamine (DFO)-mediated iron chelation, not by reserpine-mediated inhibition of PpIX-effluxing ABCG2. Finally, we found that the expression level of the gene for heme oxygenase-1 (HO-1), a heme degradation enzyme, was high in C6 GSCs, which was further up-regulated when treated with 5-ALA. Our results provide important new insights into 5-ALA-based PDD of gliomas, particularly photodetection of SP-defined GSCs by iron chelation based on their ALA-PpIX-Heme metabolism.

Nanostructured lipid carrier in photodynamic therapy for the treatment of basal-cell carcinoma

Topical photodynamic therapy (PDT) is a promising alternative for malignant skin diseases such as basal-cell carcinoma (BCC), due to its simplicity, enhanced patient compliance, and localization of the residual photosensitivity to the site of application. However, insufficient photosensitizer penetration into the skin is the major issue of concern with topical PDT. Therefore, the aim of the present study was to enable penetration of photosensitizer to the different strata of the skin using a lipid nanocarrier system. We have attempted to develop a nanostructured lipid carrier (NLC) for the topical delivery of second-generation photosensitizer, 5-amino levulinic acid (5-ALA), whose hydrophilicity and charge characteristic limit its percutaneous absorption. The microemulsion technique was used for preparing 5-ALA-loaded NLC. The mean particle size, polydispersity index, and entrapment efficiency of the optimized NLC of 5-ALA were found to be 185.2 ± 1.20, 0.156 ± 0.02, and 76.8 ± 2.58%, respectively. The results of in vitro release and in vitro skin permeation studies showed controlled drug release and enhanced penetration into the skin, respectively. Confocal laser scanning microscopy and cell line studies respectively demonstrated that encapsulation of 5-ALA in NLC enhanced its ability to reach deeper skin layers and consequently, increased cytotoxicity.

Modulation of biosynthesis of photosynthetic pigments and light-harvesting complex in wild-type and gun5 mutant of Arabidopsis thaliana during impaired chloroplast development

Plants in response to different environmental cues need to modulate the expression of nuclear and chloroplast genomes that are in constant communication. To understand the signals that are responsible for inter-organellar communication, levulinic acid (LA), an inhibitor of 5-aminolevulinic acid dehydratase, was used to suppress the synthesis of pyrrole-derived tetrapyrroles chlorophylls. Although, it does not specifically inhibit carotenoid biosynthesis enzymes, LA reduced the carotenoid contents during photomorphogenesis of etiolated Arabidopsis seedlings. The expression of nuclear genes involved in carotenoid biosynthesis, i.e., geranylgeranyl diphosphate synthase, phytoene synthase, and phytoene desaturase, was downregulated in LA-treated seedlings. Similarly, the transcript abundance of nuclear genes, i.e., Lhcb1, PsbO, and RcbS, coding for chloroplastic proteins was severely attenuated in LA-treated samples. In contrast, LA treatment did not affect the transcript abundance of chalcone synthase, a marker gene for cytoplasm, and β-ATP synthase, a marker gene for mitochondria. This demonstrates the retrograde signaling from chloroplast to nucleus to suppress chloroplastic proteins during impaired chloroplast development. However, under identical conditions in LA-treated tetrapyrrole-deficient gun5 mutant, retrograde signal continued. The tetrapyrrole biosynthesis inhibitor LA suppressed formation of all tetrapyrroles both in WT and gun5. This rules out the role of tetrapyrroles as signaling molecules in WT and gun5. The removal of LA from the Arabidopsis seedlings restored the chlorophyll and carotenoid contents and expression of nuclear genes coding for chloroplastic proteins involved in chloroplast biogenesis. Therefore, LA could be used to modulate chloroplast biogenesis at a desired phase of chloroplast development.

Evaluation of a Porcine Gastric Mucin and RNase A Assay for the Discrimination of Infectious and Non-infectious GI.1 and GII.4 Norovirus Following Thermal, Ethanol, or Levulinic Acid Plus Sodium Dodecyl Sulfate Treatments

Human noroviruses (NoVs) are a major source of foodborne illnesses worldwide. Since human NoVs cannot be cultured in vitro, methods that discriminate infectious from non-infectious NoVs are needed. The purpose of this study was to evaluate binding of NoV genotypes GI.1 and GII.4 to histo-blood group antigens expressed in porcine gastric mucin (PGM) as a surrogate for detecting infectious virus following thermal (99 °C/5 min), 70% ethanol or 0.5% levulinic acid (LV) plus 0.01 or 0.1% sodium dodecyl sulfate (SDS) sanitizer treatments and to determine the limit of detection of GI.1 and GII.4 binding to PGM. Treated and control virus samples were applied to 96-well plates coated with 1 µg/ml PGM followed by RNase A (5 ng/µl) treatment for degradation of exposed RNA. Average log genome copies per ml (gc/ml) reductions and relative differences (RD) in quantification cycle (Cq) values after thermal treatment were 1.77/5.62 and 1.71/7.25 (RNase A) and 1.73/5.50 and 1.56/6.58 (no RNase A) for GI.1 and GII.4, respectively. Treatment of NoVs with 70% EtOH resulted in 0.05/0.16 (GI.1) and 3.54/10.19 (GII.4) log reductions in gc/ml and average RD in Cq value, respectively. LV (0.5%) combined with 0.1 % SDS provided a greater decrease of GI.1 and GII.4 NoVs with 8.97 and 8.13 average RD in Cq values obtained, respectively than 0.5% LV/0.01 % SDS. Virus recovery after PGM binding was variable with GII.4 > GI.1. PGM binding is a promising surrogate for identifying infectious and non-infectious NoVs after capsid destruction, however, results vary depending on virus strain and inactivation method.

Physiological and molecular analyses of black and yellow seeded Brassica napus regulated by 5-aminolivulinic acid under chromium stress

Brassica napus L. is a promising oilseed crop among the oil producing species. So, it is prime concern to screen the metal tolerant genotypes in order to increase the oilseed rape production through the utilization of pollutant soil regimes. Nowadays, use of plant growth regulators against abiotic stress is one of the major objectives of researchers. In this study, an attempt was carried out to analyze the pivotal role of exogenously applied 5-amenolevulinic acid (ALA) on alleviating chromium (Cr)-toxicity in black and yellow seeded B. napus. Plants of two cultivars (ZS 758 - a black seed type, and Zheda 622 - a yellow seed type) were treated with 400 μM Cr with or without 15 and 30 mg/L ALA. Results showed that exogenously applied ALA improved the plant growth and increased ALA contents; however, it decreased the Cr concentration in B. napus leaves under Cr-toxicity. Moreover, exogenous ALA reduced oxidative stress by up-regulating antioxidant enzyme activities and their related gene expression. Further, results suggested that stress responsive protein's transcript level such as HSP90-1 and MT-1 were increased under Cr stress alone in both cultivars. Exogenously applied ALA further enhanced the expression rate in both genotypes and obviously results were found in favor of cultivar ZS 758. The ultrastructural changes were observed more obvious in yellow seeded than black seeded cultivar; however, exogenously applied ALA helped the plants to recover their cell turgidity under Cr stress. The present study describes a detailed molecular mechanism how ALA regulates the plant growth by improving antioxidant machinery and related transcript levels, cellular modification as well as stress related genes expression under Cr-toxicity.

Improvement of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) production by dual feeding with levulinic acid and sodium propionate in Cupriavidus necator

In the context of increasing volatility of oil prices, replacement of petroleum based plastics by bioplastics is a topic of increasing interest. Poly(hydroxyalkanoate)s (PHAs) are among the most promising families in this field. Controlling composition of the polymer on the monomeric level remains a pivotal issue. This control is even more difficult to achieve when the polymer is not synthesized by chemists, but produced by nature, in this case, bacteria. In this study mechanism and role of two 3-hydroxyvalerate (3-HV) inducing substrates on the production of PHBV with high, 80%, 3-HV content were evaluated. It was found that levulinic acid contributes to biomass and bio-polymer content enhancement, whereas sodium propionate mainly contributes to 3-HV enhancement. Optimized proportions of feeding substrates at 1 g/L and 2.5 g/L, respectively for levulinic acid and sodium propionate allowed a 100% productivity enhancement, at 3.9 mg/L/hour, for the production of PHBV with 80% 3-HV.

Bacterial production of short-chain organic acids and trehalose from levulinic acid: a potential cellulose-derived building block as a feedstock for microbial production

Levulinic acid (LA) is a platform chemical derived from cellulosic biomass, and the expansion of LA utilization as a feedstock is important for production of a wide variety of chemicals. To investigate the potential of LA as a substrate for microbial conversion to chemicals, we isolated and identified LA-utilizing bacteria. Among the six isolated strains, Pseudomonas sp. LA18T and Rhodococcus hoagie LA6W degraded up to 70 g/L LA in a high-cell-density system. The maximal accumulation of acetic acid by strain LA18T and propionic acid by strain LA6W was 13.6 g/L and 9.1 g/L, respectively, after a 4-day incubation. Another isolate, Burkholderia stabilis LA20W, produced trehalose extracellularly in the presence of 40 g/L LA to approximately 2 g/L. These abilities to produce useful compounds supported the potential of microbial LA conversion for future development and cellulosic biomass utilization.

Tolerance of the nanocellulose-producing bacterium Gluconacetobacter xylinus to lignocellulose-derived acids and aldehydes

Lignocellulosic biomass serves as a potential alternative feedstock for production of bacterial nanocellulose (BNC), a high-value-added product of bacteria such as Gluconacetobacter xylinus. The tolerance of G. xylinus to lignocellulose-derived inhibitors (formic acid, acetic acid, levulinic acid, furfural, and 5-hydroxymethylfurfural) was investigated. Whereas 100 mM formic acid completely suppressed the metabolism of G. xylinus, 250 mM of either acetic acid or levulinic acid still allowed glucose metabolism and BNC production to occur. Complete suppression of glucose utilization and BNC production was observed after inclusion of 20 and 30 mM furfural and 5-hydroxymethylfurfural, respectively. The bacterium oxidized furfural and 5-hydroxymethylfurfural to furoic acid and 5-hydroxymethyl-2-furoic acid, respectively. The highest yields observed were 88% for furoic acid/furfural and 76% for 5-hydroxymethyl-2-furoic acid/5-hydroxymethylfurfural. These results are the first demonstration of the capability of G. xylinus to tolerate lignocellulose-derived inhibitors and to convert furan aldehydes.

A novel formulation effective in killing oral biofilm bacteria

OBJECTIVE

To determine if a novel formulation is effective in killing oral biofilm streptococci in vitro and in vivo.

METHODS

Efficacy of 0.5% levulinic acid and 0.05% sodium dodecyl sulfate (SDS) in killing Streptococcus gordonii CH1, Streptococcus gordonii DL1, Streptococcus mitis NCTC10712, Streptococcus oralis KS32AR, Streptococcus mutans BM71, and Streptococcus mutans GS5 in their biofilm form was measured in vitro, using microtiter plates and subsequent counts on Mitis-Salivarius agar plates. The safety and efficacy in vivo were evaluated using a mouse model.

RESULTS

Our anti-microbial formulation completely eliminated all the biofilm streptococcal species tested within 30 seconds (a reduction of 10(7) CFU/ml), whereas the positive control Listerine only demonstrated moderate reduction in vitro. Application of the formulation twice a day for 7 days in the murine oral cavity resulted in significantly more reduction of established S. gordonii DL1 oral biofilm bacteria than Listerine. The formulation did not cause any adverse effect in the murine oral cavity within a 2-week period.

CONCLUSIONS

We have demonstrated that the novel mouth rinse exhibits high efficacy in killing oral bacteria in their biofilm forms, results in no adverse effect in vivo, and contains alcohol-free components.

Efficacy of levulinic acid-sodium dodecyl sulfate against Encephalitozoon intestinalis, Escherichia coli O157:H7, and Cryptosporidium parvum

Foodborne parasites are characterized as being highly resistant to sanitizers used by the food industry. In 2009, a study reported the effectiveness of levulinic acid in combination with sodium dodecyl sulfate (SDS) in killing foodborne bacteria. Because of their innocuous properties, we studied the effects of levulinic acid and SDS at various concentrations appropriate for use in foods, on the viability of Cryptosporidium parvum and Encephalitozoon intestinalis. The viability of Cryptosporidium and E. intestinalis was determined by in vitro cultivation using the HCT-8 and RK-13 cell lines, respectively. Two Escherichia coli O157:H7 isolates were also used in the present study: strain 932 (a human isolate from a 1992 Oregon meat outbreak) and strain E 0018 (isolated from calf feces). Different concentrations and combinations of levulinic acid and SDS were tested for their ability to reduce infectivity of C. parvum oocysts (10(5)), E. intestinalis spores (10(6)), and E. coli O157:H7 (10(7)/ml) when in suspension. Microsporidian spores were treated for 30 and 60 min at 20 ± 2°C. None of the combinations of levulinic acid and SDS were effective at inactivating the spores or oocysts. When Cryptosporidium oocysts were treated with higher concentrations (3% levulinic acid-2% SDS and 2% levulinic acid-1% SDS) for 30, 60, and 120 min, viability was unaffected. E. coli O157:H7, used as a control, was highly sensitive to the various concentrations and exposure times tested. SDS and levulinic acid alone had very limited effect on E. coli O157:H7 viability, but in combination they were highly effective at 30 and 60 min of incubation. In conclusion, Cryptosporidium and microsporidia are not inactivated when treated for various periods of time with 2% levulinic acid-1% SDS or 3% levulinic acid-2% SDS at 20°C, suggesting that this novel sanitizer cannot be used to eliminate parasitic contaminants in foods.

Acids in combination with sodium dodecyl sulfate caused quality deterioration of fresh-cut iceberg lettuce during storage in modified atmosphere package

Recent studies showed that sodium acid sulfate (SAS) and levulinic acid (LA) in combination with sodium dodecyl sulfate (SDS) was effective in inactivating human pathogens on Romaine lettuce. The present study investigated the effects of LA and SAS in combination with SDS (as compared with citric acid and chlorine) on the inactivation of E. coli O157:H7 and sensory quality of fresh-cut Iceberg lettuce in modified atmosphere packages during storage at 4 °C. Results showed that LA (0.5% to 3%) and SAS (0.25% to 0.75%) with 0.05% SDS caused detrimental effects on visual quality and texture of lettuce. LA- and SAS-treated samples were sensorially unacceptable due to development of sogginess and softening after 7 and 14 d storage. It appears that the combined treatments caused an increase in the respiration rate of fresh-cut lettuce as indicated by higher CO(2) and lower O(2) in modified atmosphere packages. On the positive side, the acid treatments inhibited cut edge browning of lettuce pieces developed during storage. LA (0.5%), SAS (0.25%), and citric acid (approximately 0.25%) in combination with SDS reduced population of E. coli OH157:H7 by 0.41, 0.87, and 0.58 log CFU/g, respectively, while chlorine achieved a reduction of 0.94 log CFU/g without damage to the lettuce. Therefore, compared to chlorine, LA and SAS in combination with SDS have limited commercial value for fresh-cut Iceberg lettuce due to quality deterioration during storage.

Inactivation of Salmonella and Escherichia coli O157:H7 on lettuce and poultry skin by combinations of levulinic acid and sodium dodecyl sulfate

Four organic acids (lactic acid, acetic acid, caprylic acid, and levulinic acid) and sodium dodecyl sulfate (SDS) were evaluated individually or in combination for their ability to inactivate Salmonella and Escherichia coli O157:H7. Results from pure culture assays in water with the treatment chemical revealed that 0.5% organic acid and 0.05 to 1% SDS, when used individually, reduced pathogen cell numbers by < or = 2 log CFU/ml within 20 min at 21 degrees C. The combination of any of these organic acids at 0.5% with 0.05% SDS resulted in > 7 log CFU/ml inactivation of Salmonella and E. coli O157:H7 within 10 s at 21 degrees C. A combination of levulinic acid and SDS was evaluated at different concentrations for pathogen reduction on lettuce at 21 degrees C, on poultry (wings and skin) at 8 degrees C, and in water containing chicken feces or feathers at 21 degrees C. Results revealed that treatment of lettuce with a combination of 3% levulinic acid plus 1% SDS for < 20 s reduced both Salmonella and E. coli O157:H7 populations by > 6.7 log CFU/g on lettuce. Salmonella and aerobic bacterial populations on chicken wings were reduced by > 5 log CFU/g by treatment with 3% levulinic acid plus 2% SDS for 1 min. Treating water heavily contaminated with chicken feces with 3% levulinic acid plus 2% SDS reduced Salmonella populations by > 7 log CFU/ml within 20 s. The use of levulinic acid plus SDS as a wash solution may have practical application for killing foodborne enteric pathogens on fresh produce and uncooked poultry.

[Purification and production of the extracellular 5-aminolevulinate from recombiniant Escherichia coli expressing yeast ALAS]

Aminolevulinic acid (ALA) is biosynthesized by the enzyme ALA synthase (ALAS). The ALA production has been studied using the overproducing ALAS from several bacteria in Escherchia coil, respectively. However, ALAS from eucaryote expressed in E. coli for producing ALA in the culture is not known. The extracellular ALA production and cell growth were investageted respectively using the recombinant E. coli overproducing Saccharomyces cerevisiae ALAS in shake-flask fermentations. The ALAS activity from the cell extract was assayed. The extracellular ALA was purified by the national-made large-dimension resins and confirmed by the capillary electrophoresis measurements. At 12h after induction at 37 degrees C, the extracellular ALA production was up to 162mg per liter LB culture at initial pH 6.5 with exogenous levulinate, succinate and and glycine at the concentration of 20 mmol/L respectively. The purity of ALA after purification is up to 90%.

Biosynthesis of intracellular 5-aminolevulinic acid by a newly identified halotolerant Rhodobacter sphaeroides

Of 23 strains of halotolerant (up to 12% w/v NaCl) photosynthetic bacteria isolated from various sources, one isolate, SH5, accumulated intracellular 5-aminolevulinic acid (ALA) at 0.45 microg/g dry cell wt (DCW) growing aerobically in the dark. The strain was identified as Rhodobacter sphaeroides using 16S rDNA sequencing. Biosynthesis of ALA was enhanced to 14 microg/g DCW using modified glutamate/glucose (50 mM) medium with the addition of 10 mM levulinic acid after 24 h cultivation. Addition of 30 microM Fe(2+) to this medium increased the yield to 226 microg/g DCW.

Porphobilinogen synthase from the butterfly, Pieris brassicae: purification and comparative characterization

Porphobilinogen represents a key building block of tetrapyrroles serving as functional ligands of many vitally important proteins. Here we report the first purification of porphobilinogen synthase (PBGS) from whole insects by sequentially employing two modes of native electrophoresis on polyacrylamide gels subsequent to more conventional procedures. Using adults of Pieris brassicae L. (Lepidoptera: Pieridae) we achieved approximately 10,000-fold purification with final yields of up to 25% of electrophoretically pure PBGS with a specific activity of approximately 160 micromol PBG h(-1) mg(-1) at 37 degrees C and an affinity of 0.36 mM to its substrate 5-aminolevulinic acid. Enzyme activity was inhibited by the substrate mimics, levulinic acid and succinylacetone, and by chelating agents. PBGS behaved as a relatively heat-stable octameric complex of 292.3 kDa composed of 36.5 kDa subunits. Most general features of this insect PBGS were comparable to those published for other animal PBGS enzymes, while remarkable differences were found to the reported recombinant Drosophila enzyme. Moreover, rabbit antiserum directed against purified Pieris PBGS revealed significant immunological differences among insect PBGS enzymes from a wide range of orders contrasting to the overall evolutionary conserved features of this enzyme.

Industry research on the use and effects of levulinic acid: A case study in cigarette additives

Public health officials and tobacco researchers have raised concerns about the possible contributions of additives to the toxicity of cigarettes. However, little attention has been given to the process whereby additives promote initiation and addiction. Levulinic acid is a known cigarette additive. Review of internal tobacco industry documents indicates that levulinic acid was used to increase nicotine yields while enhancing perceptions of smoothness and mildness. Levulinic acid reduces the pH of cigarette smoke and desensitizes the upper respiratory tract, increasing the potential for cigarette smoke to be inhaled deeper into the lungs. Levulinic acid also may enhance the binding of nicotine to neurons that ordinarily would be unresponsive to nicotine. These findings held particular interest in the internal development of ultralight and so-called reduced-exposure cigarette prototypes. Industry studies found significantly increased peak plasma nicotine levels in smokers of ultralight cigarettes following addition of levulinic acid. Further, internal studies observed changes in mainstream and sidestream smoke composition that may present increased health risks. The use of levulinic acid illustrates the need for regulatory authority over tobacco products as well as better understanding of the role of additives in cigarettes and other tobacco products.