PARG dysfunction enhances DNA double strand break formation in S-phase after alkylation DNA damage and augments different cell death pathways

Poly(ADP-ribose) glycohydrolase (PARG) is the primary enzyme responsible for the degradation of poly(ADP-ribose). PARG dysfunction sensitizes cells to alkylating agents and induces cell death; however, the details of this effect have not been fully elucidated. Here, we investigated the mechanism by which PARG deficiency leads to cell death in different cell types using methylmethanesulfonate (MMS), an alkylating agent, and Parg^−/− mouse ES cells and human cancer cell lines. Parg^−/− mouse ES cells showed increased levels of γ-H2AX, a marker of DNA double strand breaks (DSBs), accumulation of poly(ADP-ribose), p53 network activation, and S-phase arrest. Early apoptosis was enhanced in Parg^−/− mouse ES cells. Parg^−/− ES cells predominantly underwent caspase-dependent apoptosis. PARG was then knocked down in a p53-defective cell line, MIAPaCa2 cells, a human pancreatic cancer cell line. MIAPaCa2 cells were sensitized to MMS by PARG knockdown. Enhanced necrotic cell death was induced in MIAPaCa2 cells after augmenting γ-H2AX levels and S-phase arrest. Taken together, these data suggest that DSB repair defect causing S-phase arrest, but p53 status was not important for sensitization to alkylation DNA damage by PARG dysfunction, whereas the cell death pathway is dependent on the cell type. This study demonstrates that functional inhibition of PARG may be useful for sensitizing at least particular cancer cells to alkylating agents.

Mesenteric phlebosclerosis associated with long-term oral intake of geniposide, an ingredient of herbal medicine

BACKGROUND

Idiopathic mesenteric phlebosclerosis (IMP) is a rare disease, characterised by thickening of the wall of the right hemicolon with calcification of mesenteric veins. However, the aetiology remains unknown.

AIM

To investigate the possible association of herbal medicines with IMP.

METHOD

The clinical data of four of our own patients were collected. Furthermore, we searched for previous reports about similar patients with detailed descriptions of herbal prescriptions that they had taken. We compared herbal ingredients to identify the toxic agent as a possible aetiological factor.

RESULTS

Clinical data on a total of 25 patients were summarised. Mean age was 61.8 years and there was female predominance (6 men and 19 women). The used Kampo prescription, the number of cases, and the mean duration of use were as follows: kamisyoyosan in 12 cases for 12.8 years, inshin-iseihaito in 5 cases for 13.4 years, orengedokuto in 4 cases for 14.3 years, inchinkoto in 1 case for 20 years, kamikihitou in 1 case for 19 years, seijobofuto in 1 case for 10 years and gorinsan in 1 case for an unknown duration. Only one ingredient, sansisi, was common to the herbal medicines of all 25 patients. This crude drug called geniposide in English is a major constituent of the Gardenia fruits.

CONCLUSION

The long-term use of geniposide in herbal medicines appears to be associated with mesenteric phlebosclerosis.

[Aortic dissection with ischemia of the abdominal organs]

Abdominal organ ischemia associated with aortic dissection is a serious problem, although its incidence is not so high. In particular, the prognosis of bowel ischemia is extremely poor, especially, in cases with the diagnosis delayed and with extensive bowel ischemia. Consequently, 1st it should be suspected, in cases with abdominal pain or distension associated with acute or chronic aortic dissection. Then, its pathology should be assessed quickly with enhanced computed tomography (CT) or ultrasound examination to clarify the mechanism of critical organ ischemia including dynamic obstruction or static obstruction of the visceral arteries. According to the mechanism of abdominal organ ischemia, the best treatment of catheter interventions such as catheter fenestration, endovascular aortic repair, and branch-stenting, or of conventional open surgery such as surgical abdominal aortic fenestration, graft replacement, and branch-bypass should be appropriately chosen without delay.

Improvement in organic solvent tolerance by double disruptions of proV and marR genes in Escherichia coli

AIMS

To investigate the involvement of osmoprotectant transporters in organic solvent tolerance in Escherichia coli and to construct an E. coli strain with high organic solvent tolerance.

METHODS AND RESULTS

The organic solvent tolerance of ΔbetT, ΔproV, ΔproP or ΔputP single-gene knockout mutants of E. coli K-12 strain was examined. Among these mutants, the organic solvent tolerance of the ΔproV mutant remarkably increased compared with that of the parent strain. It has been known that a marR mutation confers tolerance on E. coli to organic solvents. A ΔproV and ΔmarR double-gene mutant was more tolerant to organic solvents than the ΔproV or ΔmarR single-gene mutant. The n-hexane amount accumulated in E. coli cells was examined after incubation in an n-hexane-aqueous medium two-phase system. The intracellular n-hexane level in the ΔproV and ΔmarR double-gene mutant was kept lower than those of the parent strain, ΔproV mutant and ΔmarR mutant.

CONCLUSIONS

The organic solvent tolerance level in E. coli highly increased by dual disruption of proV and marR.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study suggests a new strategy for increasing the organic solvent tolerance level in E. coli to improve the usability of the whole-cell biocatalysts in two-phase systems employing organic solvents.

Use of the triaxial microcatheter method in super-selective transcatheter arterial chemoembolisation for hepatocellular carcinoma

OBJECTIVES

Transcatheter arterial chemoembolisation (TACE) has been widely used for inoperable hepatocellular carcinoma (HCC). Super-selective TACE is preferable to non-selective therapy, because it maximises the impact of treatment on the tumour while minimising damage to tumour-free liver parenchyma. It is therefore important to advance the catheter tip as close as possible in the feeding artery. There is now a new microcatheter with a 1.9-Fr tip with no taper, which can be inserted into a 2.7-Fr microcatheter. In this study we describe the new technique of using the two microcatheters called the triaxial microcatheter method.

METHODS

We evaluated 30 TACE procedures to investigate whether or not the catheter tip could be advanced closer to HCC with the triaxial microcatheter method than with previous TACE using a conventional microcatheter.

RESULTS

With conventional microcatheters, the level of embolisation was a lobar artery in 4 cases, segmental in 8 cases, subsegmental in 15 cases and sub-subsegmental in only 1 case. TACE could not be performed in two cases. When using the triaxial microcatheter method the level of embolisation was subsegmental in 8 cases, including 2 in which the level was the same as that with a conventional microcatheter, sub-subsegmental in 13 cases and more distal in 7 cases. In the two cases in which TACE could not be performed with the conventional microcatheter, it could be performed sufficiently using the new method. As a whole, in 28 of the 30 procedures (93%) we could successfully advance a catheter tip closer than with the previous TACE.

CONCLUSION

The triaxial microcatheter method appears to be useful.

Multiple ulcers in the small and large intestines occurred during tocilizumab therapy for rheumatoid arthritis

Tocilizumab is a monoclonal antibody against human interleukin-6 receptor which blocks the binding of interleukin-6 to its receptor. Tocilizumab is effective for the treatment of inflammatory disorders including rheumatoid arthritis. We report a case of multiple ulcers in the small and large intestines, which occurred during tocilizumab therapy. A 57-year-old woman started to use tocilizumab for rheumatoid arthritis. Three months later, she complained of hematochezia. Double-balloon endoscopy revealed multiple small aphthoid ulcers in the small and large intestines. One month after the woman had recovered, she was given tocilizumab again. The woman had hematochezia and abdominal pain again 2 weeks later. Colonoscopy revealed multiple round, discrete punched-out ulcers in the terminal ileum, and vast deep ulcers from the cecum to the descending colon. Bioptic histopathology and cultivation showed non-specific findings. Six weeks after discontinuation of tocilizumab, ulcers in the small and large intestine dramatically improved, leaving ulcer scars. This disease course and the results of examination made us strongly suspect that tocilizumab induced multiple ulcers in the small and large intestines. Interleukin-6 is a pleiotropic cytokine and involved in intestinal mucosal wound healing as well as in inflammatory processes. It is possible that tocilizumab inhibited tissue repair of the intestine and caused intestinal ulcers.

Organic-solvent-tolerant bacterium which secretes organic-solvent-stable lipolytic enzyme

A bacterial strain which could be grown in a medium containing organic solvents and which could secrete lipolytic enzyme was isolated. The stability of the lipolytic activity of the supernatant of the culture increased significantly in the presence of organic solvents such as toluene, cyclohexane, ethanol, and acetone.

Poly(ADP-ribose) Glycohydrolase deficiency sensitizes mouse ES cells to DNA damaging agents

Poly(ADP-ribose) glycohydrolase (Parg) is the main enzyme for degradation of poly(ADP-ribose) by splitting ribose-ribose bonds. Parg-deficient (Parg(+/-) and Parg(-/-)) mouse ES cell lines have been established by disrupting both alleles of Parg exon 1 through gene-targeting. A transcript encoding a full length isoform of Parg was eliminated and only low amounts of Parg isoforms were detected in Parg(-/-) embryonic stem (ES) cells. Poly(ADP-ribose) degradation activity was decreased to one-tenth of that in Parg(+/+) ES cells. Parg(-/-) ES cells exhibited the same growth rate as Parg(+/+) ES cells in culture. Sensitivity of Parg(-/-) ES cells to various DNA damaging agents, including an alkylating agent dimethyl sulfate, cisplatin, gemcitabine, 5-fluorouracil, camptothecin, and gamma-irradiation was examined by clonogenic survival assay. Parg(-/-) ES cells showed enhanced lethality after treatment with dimethyl sulfate, cisplatin and gamma-irradiation compared with wild-type (Parg(+/+)) ES cells (p<0.05, respectively). In contrast, a sensitization effect by Parg-deficiency was not observed with gemcitabine and camptothecin. These results suggest the possibility that functional inhibition of Parg leads to sensitization of tumor cells to some chemo- and radiation therapies.

Persistent gut motor dysfunction in a murine model of T-cell-induced enteropathy

BACKGROUND

Inflammatory bowel disease (IBD) patients in remission often experience irritable bowel syndrome (IBS)-like symptoms. We investigated the mechanism for intestinal muscle hypercontractility seen in T-cell-induced enteropathy in recovery phase.

METHODS

BALB/c mice were treated with an anti-CD3 antibody (100 microg per mouse) and euthanized at varying days post-treatment to investigate the histological changes, longitudinal smooth muscle cell contraction, cytokines (Th1, Th2 cytokines, TNF-alpha) and serotonin (5-HT)-expressing enterochromaffin cell numbers in the small intestine. The role of 5-HT in anti-CD3 antibody-induced intestinal muscle function in recovery phase was assessed by inhibiting 5-HT synthesis using 4-chloro-DL-phenylalanine (PCPA).

KEY RESULTS

Small intestinal tissue damage was observed from 24 h after the anti-CD3 antibody injection, but had resolved by day 5. Carbachol-induced smooth muscle cell contractility was significantly increased from 4 h after injection, and this muscle hypercontractility was evident in recovery phase (at day 7). Th2 cytokines (IL-4, IL-13) were significantly increased from 4 h to day 7. 5-HT-expressing cells in the intestine were increased from day 1 to day 7. The 5-HT synthesis inhibitor PCPA decreased the anti-CD3 antibody-induced muscle hypercontractility in recovery phase.

CONCLUSIONS & INFERENCES

Intestinal muscle hypercontractility in remission is maintained at the smooth muscle cell level. Th2 cytokines and 5-HT in the small intestine contribute to the maintenance of the altered muscle function in recovery phase.

[Long-term outcome of aortic valve sparing procedures in connective tissue disorders]

OBJECTIVES

The aim of this study is to determine the long-term outcome of aortic valve sparing procedures for patients having connective tissue disorder.

METHODS

Between 1993 and 2008, the aortic valve sparing surgery was performed in 94 patients having aortic root dilatation. Eighty patients of them (37.2 +/- 13.4 years, 50 male) had cystic medial necrosis in the aortic wall, which was confirmed the pathological examination. We reviewed these patients. Sixty percent (48/80) had Marfan syndrome, 5% (4/80) had Loeyz-Dietz syndrome, 2% (2/80) had bicuspid aortic valve, and 11% (9/80) had aortic dissection. Our reimplantation procedure has been refined as followed: with a tube graft in 41, a tube graft with creation of neo-sinuses in 11, and a Valsalva graft in 14. Fourteen patients underwent the remodeling procedure. The follow-up rate was 100% with the duration of 3.7+/- 3.4 years.

RESULTS

There were no operative death but six late deaths. Seventeen (21.3%) patients required aortic valve replacement, for recurrent aortic insufficiency in 13 and infection in 4. Freedom from reoperation was 80%, 43%, and freedom from moderate or severe aortic insufficiency was 80%, 54%, at 5 and 10 years, respectively. Pathological findings of the aortic valve obtained in the reoperations showed elongation and prolapse of the aortic valve due to myxomatous degeneration and fibrous thickening caused by aortic insufficiency.

CONCLUSIONS

Even in connective tissue disorders, aortic valve sparing operation is associated with acceptable long-term durability, although cusp degeneration resulting in recurrent aortic insufficiency might be progressive.

Involvement of tazarotene-induced gene 1 in proliferation and differentiation of human adipose tissue-derived mesenchymal stem cells

OBJECTIVE

Mesenchymal stem cells (MSC) have both self-renewal and multilineage differentiation potential, and bone marrow-derived MSC have been applied for tissue regeneration and repair. Although adipose tissue-derived MSC (ASC) have emerged as an alternative cell source, little information is available regarding the biologic difference between ASC derived from visceral and subcutaneous fat. Therefore, we aimed to compare the proliferation and gene expression profile of cultured human visceral ASC (VASC) and subcutaneous ASC (SASC), and to identify a novel gene involved in proliferation and differentiation of ASC.

MATERIALS AND METHODS

We performed microarray analysis of cultured VASC and SASC, and investigated the role of tazarotene-induced gene 1 (TIG1), a most differentially expressed gene, in the proliferation and differentiation of ASC.

RESULTS

SASC proliferated faster than VASC for over 10 passages, and TIG1 expression was consistently up-regulated in VASC of humans, rats and mice. Overexpression of the TIG1 gene in human SASC inhibited cell proliferation, whereas knockdown of TIG1 expression by siRNA promoted cell proliferation. In addition, overexpression of the TIG1 gene in SASC enhanced their differentiation into adipocytes, and promoted up-regulation of peroxisome proliferators-activated receptor gamma and CCAAT/enhancer binding protein alpha. On the other hand, TIG1 overexpression in SASC inhibited their differentiation into osteocytes and the expression of osteocalcin.

CONCLUSION

TIG1 plays an important role in regulating proliferation and differentiation of ASC.

Impact of double-balloon endoscopy on the diagnosis of jejunoileal involvement in primary intestinal follicular lymphomas: a case series

In recent years, primary gastrointestinal follicular lymphoma has been increasingly detected in the duodenum on esophagogastroduodenoscopy (EGD). Primary gastrointestinal follicular lymphomas are frequently distributed to multiple sites in the gastrointestinal tract. Therefore, investigation into the spread of follicular lymphomas in the small bowel is important in order to determine the most appropriate treatment strategy. The performance of double-balloon endoscopy (DBE) in the diagnosis of jejunoileal follicular lymphoma lesions has not been fully evaluated. We aimed to investigate the value of DBE in addition to computed tomography (CT) and (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) in the diagnosis of jejunoileal follicular lymphoma. DBE with biopsy was performed in seven patients with primary duodenal follicular lymphoma diagnosed by EGD, in order to investigate jejunoileal involvement. Jejunoileal follicular lymphoma lesions were detected by DBE in six out of the seven patients (three in the jejunum and three in the jejunum and ileum), whereas CT and (18)F-FDG-PET failed to detect the existence of these lesions. Endoscopic findings of the jejunoileal lesions revealed multiple white nodules and white villi, which were similar to those of duodenal lesions. DBE was more useful for the diagnosis of jejunoileal involvement in primary intestinal follicular lymphoma than CT and (18)F-FDG-PET. The use of DBE will become important for determining the most appropriate treatment for gastrointestinal follicular lymphoma.

Cetilistat (ATL-962), a novel pancreatic lipase inhibitor, ameliorates body weight gain and improves lipid profiles in rats

Cetilistat is a novel inhibitor of pancreatic lipase. The aim of this report is to evaluate the anti-obesity action of cetilistat in diet-induced obesity (DIO) rats. Cetilistat inhibited rat and human pancreatic lipase activity with an IC (50) of 54.8 nmol/l, and 5.95 nmol/l, respectively, meaning that it is 9.2 times more potent for human pancreatic lipase than for that of rat. Cetilistat was orally administered simultaneously with fat emulsion to Sprague-Dawley rats. Plasma triglyceride (TG) concentrations were measured before and after oral fat loading. The elevation in plasma triglyceride concentration by oral fat loading was reduced by cetilistat in a dose-dependent manner at 3, 10, 30, and 100 mg/kg, indicating that cetilistat reduces intestinal fat absorption in rats. Cetilistat was administered to DIO F344 rats as food admixture in a high-fat diet at 4.9, 14.9, or 50.7 mg/kg/day for three weeks. Both triglyceride and nonesterified fatty acid content in the feces were dose-dependently and drastically increased, suggesting the intestinal breakdown of fat and excretion. Body weight (BW) gain and white adipose tissue (WAT) weight were reduced in a dose-dependent manner. In addition, leptin, TG, and total cholesterol (TC) in plasma were reduced and there were no reports of oily stools. These results suggest that cetilistat ameliorates obesity and hyperlipidemia in DIO rats, a plausible animal model of the most common type of human obesity.

Masked Prosthetic Graft to Sigmoid Colon Fistula Diagnosed by 18-fluorodeoxyglucose Positron Emission Tomography

The diagnosis of low grade prosthetic graft infection or aorto-enteric fistula is difficult using conventional radiographic imaging modalities. We report a case of aorto-enteric fistula to the sigmoid colon diagnosed by the new technique of 18-fluorodeoxyglucose positron emission tomography.

Embolization for asymptomatic aneurysms of the first jejunal artery

In a 71-year-old man with a history of coronary artery bypassing using the left internal thoracic and gastroepiploic arteries, the first jejunal artery aneurysms were found by chance at 3D-CT performed to evaluate conditions of the grafts. He was successfully treated by transcatheter embolization using interlocking detachable coils. During a follow-up period of 5 months, the patient did well and had no sign of intestinal ischemia.

Quantitative RT-PCR analysing expression of gefitinib resistance related genes predicts clinical outcome of non-small cell lung cancer patients treated with gefitinib

7181

Background: Gefitinib, an inhibitor of epidermal growth factor receptor-tyrosine kinase, has shown favorable anti-tumor activity to a subset of patients with advanced non-small cell lung cancer (NSCLC). However, gefitinib failed to significantly prolong survival in comparison to placebo in unselected population. Consequently, selection of patients who will benefit from this treatment is clinically important. In the previous study, we identified gefitinib-resistance related genes (GRRGs) by cDNA microarray analyses and reported that the responsiveness of individual patients with NSCLC to gefitinib could be predicted by expression of GRRGs. The goal of this study is to establish clinically adoptive prediction system of clinical outcome of NSCLC patients treated by gefitinib. Methods: Tumors from 30 NSCLC patients treated daily with 250mg of gefitinib were evaluated for the expression of GRRGs by quantitative RT-PCR. Gefitinib response score (GRS) reflecting gene expression was calculated based on weighted vote method and this numerical scoring system was validated by leave-one-out approach and independent test cases. Results: The sensitivity of 15 learning cases (five partial response (PR) cases and 10 progressive disease (PD) cases) were predicted by leave-one-out cross validation with 93.3% (14/15) accuracy. This numerical scoring system correctly predicted responses to the drug in all of nine additional test cases (three PR cases and six PD cases). Notably, this system also could predict two stable disease (SD) cases who successfully controlled by gefitinib more than four months as responder. On the other hand, four patients who had been judged as SD but showed progression of the disease within three months were judged as non-responders. Moreover, gefitinib-treated patients with good signature had a statistically significant improvement in time to progression, and survival compared with patients with bad signature (13.0 vs 1.7 months, P < .0001; 27.7 vs 6.6 months, P = .0007, respectively). Conclusions: Our results suggest that clinical outcome of NSCLC patients treated with gefitinib could be predicted by expression levels of GRRGs determined by quantitative RT-PCR analyses.

No significant financial relationships to disclose.

Microalbuminuria and deterioration of renal function after elective repair of infrarenal abdominal aortic aneurysm

AIMS

Renal dysfunction affects the prognosis of patients after aortic surgery. However, the factors associated with the postoperative deterioration of renal function has not been clarified precisely.

METHOD

We prospectively examined renal function in 80 patients (age: 73 +/- 7 years, 66 males) who required the elective repair of infrarenal abdominal aortic aneurysm (AAA). Serum creatinine (Scr) was measured. 24-h-creatinine clearance (Ccr) and urinary albumin excretion (UAE) were determined. Renal volume and mean renal length were calculated using the data obtained by ultrasonography. 48 patients showed normal UAE (< 30 mg/day), and 24 had microalbuminuria (30-300 mg/day) and 8 had overt proteinuria (> 300 mg/day). Scr were 0.9 +/- 0.4, 1.0 +/- 0.3 and 2.1 +/- 1.3 mg/dl, respectively.

RESULTS

On Day 5 after surgery, 12 patients (15%) showed deterioration of renal function as defined either by an increase in Scr (> or = 0.5 mg/dl) or by a decrease in Ccr > or =20%). The acute deterioration of renal function was related to mean renal volume, mean renal length, duration of operation and the use of antibiotics. At Month 12 after surgery, Scr increased in the overt proteinuria group. The deterioration of renal function at Month 12 was found in 8 patients (10%) with microalbuminuria or overt proteinuria, and related to preoperative Ccr, UAE, mean renal volume, mean renal length, smoking status and blood pressure.

CONCLUSION

We conclude that the deterioration of renal function occurred in considerable number of patients with AAA after elective operation on acute and chronic phase, although the development of end-stage renal failure is rare. Factors related to the acute and late deterioration appears to be different. UAE and renal size should be measured, even if Scr is in normal range at preoperative observation.

Evaluation of preclinical atherosclerosis by flow-mediated dilatation of the brachial artery and carotid artery analysis in patients with a history of Kawasaki disease

Cardiac sequelae of Kawasaki disease are an important cause of ischemic heart disease in young adults. The possibility of early progression of atherosclerosis following Kawasaki disease is therefore of great concern. We examined whether preclinical atherosclerotic changes are seen in patients with a history of Kawasaki disease, and whether these changes appear in all or in only a proportion of patients. Sixty-five patients with a history of Kawasaki disease, aged 13.1 +/- 2.1 years, and 20 aged-matched controls participated in the study. All subjects underwent flow-mediated dilatation (FMD) of the brachial artery and analysis of carotid artery size and pulse-wave transmission. Patients were classified into four groups depending on the severity of the maximum coronary artery lesion: group 0 (normal), group 1 (mild), group 2 (moderate), and group 3 (severe). There was no statistical difference in the carotid artery analyses between the four groups. FMD (mean +/- SD) was significantly lower in groups 2 and 3 than in groups 0 and 1 and the control group (group 0, 19.4 +/- 3.9%; group 1, 19.5 +/-4.1%; group 2, 8.9 +/- 2.8%; group 3, 4.2 +/- 1.5%; control group, 18.8 +/- 2.8%; p < 0.0001). There was a significantly negative correlation between the severity of the coronary artery lesion and FMD (p < 0.0001 for both). Endothelial dysfunction was revealed by FMD in patients with persistent coronary artery lesions subsequent to Kawasaki disease. Preclinical atherosclerosis may be present only in patients with coronary aneurysms.

Enzymes which are stable in the presence of organic solvents

There are numerous advantages of employing enzymes as catalysts in organic solvents or aqueous solutions containing organic solvents instead of water. A few natural enzymes which are stable in the presence of organic solvents have been discovered. However, almost all natural enzymes are easily denatured and inactivated in the presence of organic solvents. Therefore, several physical and chemical methods, such as immobilization, modification, and entrapment, for stabilizing enzymes in the presence of organic solvents were developed. Protein engineering using site directed mutagenesis and directed evolution are useful for clarifying why organic solvent-stable enzymes are stable in the presence of organic solvents and for developing organic solvent-stable mutant enzymes.

Experimental investigation of fructose 1,6-diphosphate production and simultaneous ATP regeneration by conjugated enzymes in an ultrafiltration hollow-fiber reactor

The enzymatic synthesis of fructose 1,6-diphosphate (FDP) from glucose and the enzymatic ATP regeneration were performed simultaneously in an ultrafiltration hollow-fiber reactor using both the purified enzymes and the crude cell extract of Bacillus stearothermophilus. The process consisted of the three-step synthetic reactions catalyzed by glucokinase, phosphoglucose isomerase and phosphofructokinase, and the ATP regeneration reaction catalyzed by acetate kinase. The experimental results of the yield and the recycle number agreed well with the theoretical predictions calculated using a computer program developed in our preceding study. This proved the validity of this computer program for predicting or analyzing the reactor performance.

Effect of additives on transesterification activity of Rhizopus chinensis lipase

The transesterification activity of powder lipase prepared from the purified lipase of Rhizopus chinensis cells by freeze-drying was quite low compared with that of acetone-dried cells. Additives which could enhance the transesterification activity of the freeze-dried powder lipase were screened. The freeze-dried lipases prepared with certain fatty acid methylesters or certain types of surfactants exhibited high transesterification activity. It was shown that not only the solubility of the freeze-dried lipase in n-hexane but also the organic solvent-stability was enhanced when methyl stearate was added to the lipase solution at the freeze-drying step.

Lipase production in two-step fed-batch culture of organic solvent-tolerant Pseudomonas aeruginosa LST-03

Efficient lipase production by two-step fed-batch culture of an organic solvent-tolerant bacterium, Pseudomonas aeruginosa LST-03, was investigated. When FB synthetic medium was used in flask culture, no lipase activity was detected, whereas lipase was produced at 2.3 I.U./ml in C2 complex medium. However, lipase production was induced in FB medium when a fatty acid was added to the culture broth in the stationary phase. Among fatty acids tested, long chain saturated fatty acids, such as C18 (stearic acid) and C20 (arachidic acid), were found to function as effective inducers for the production of lipase, giving an activity level almost the same as that obtained in C2 medium in flask culture. Two-step lipase production, comprised of a growth phase in fed-batch mode and a production phase in which lipase was induced by the addition of 5% (v/v) stearic acid, was carried out in a jar-fermentor. In the growth phase, the maximum cell concentration at 16 h was only 20 in terms of the optical density at 660 nm (OD660), and a low level of lipase production (8 I.U./ml) was obtained after 167 h. This was considered to be due to the exhaustion of several medium components brought about by the use of an unsuitable medium or feeding solution. After analyzing the contents of the compounds in the culture broth by inductively coupled plasma spectrometry for metal ions and HPLC for anions, a modified FB medium was designed. When this modified FB medium was used in two-step fed-batch culture, the maximum cell concentration reached an OD660 of 55 (30.2 g-dry cells/l) at 16.5 h, and lipase was produced at 96 I.U./ml after 35 h, which is approximately 40 times higher than the production level obtained in flask culture using C2 medium.

Cloning, expression and characterization of a lipase gene (lip3) from Pseudomonas aeruginosa LST-03

A lipase gene (lip3) was cloned from the Pseudomonas aeruginosa strain LST-03 (which tolerates organic solvents) and expressed in Escherichia coli. The cloned sequence includes an ORF consisting of 945 nucleotides, encoding a protein of 315 amino acids (Lip3 lipase, 34.8 kDa). The predicted Lip3 lipase belongs to the class of serine hydrolases; the catalytic triad consists of the residues Ser-137, Asp-258, and His-286. The gene cloned in the present study does not encode the LST-03 lipase, a previously isolated solvent-stable lipase secreted by P. aeruginosa LST-03, because the N-terminal amino acid sequence of the Lip3 lipase differs from that of the LST-03 lipase. Although the effects of pH on the activity and stability of the Lip3 lipase, and the temperature optimum of the enzyme, were similar to those of the LST-03 lipase, the relative activity of the Lip3 lipase at lower temperatures (0-35 degrees C) was higher than that of the LST-03 lipase. In the absence of organic solvents, the half-life of the Lip3 lipase was similar to that of the LST-03 lipase. However, in the presence of most of the organic solvents tested in this study (the exceptions were ethylene glycol and glycerol), the stability of the Lip3 lipase was lower than that of the LST-03 lipase.