l-Glutamate Enhances the Expression of Thermus Maltogenic Amylase in Escherichia coli

Escherichia coli BL21 (DE3) transformed with a thermostable Thermus maltogenic amylase (ThMA), isolated from a Gram-negative bacterium Thermus strain IM6501, grew well and efficiently produced ThMA in a complex medium but not in a chemically defined medium (DM). By supplementing L-glutamate to DM medium, both the specific growth rate and ThMA expression significantly increased. Alterations in the cellular responses of recombinant E. coli to L-glutamate were analyzed at the protein level by two-dimensional gel electrophoresis and mass spectrometry. The ppGpp synthase (RelA) was significantly reduced in cells grown with L-glutamate and was consistent with the low level of ppGpp, an indicator of stringent response. On the other hand, protein chain elongation factor (EF-Tu) and manganese-containing superoxide dismutase (MnSOD), which protects cells against oxidative damage, was significantly elevated by L-glutamate supplementation. These results indicate that L-glutamate enhances ThMA expression and increases the E. coli growth rate not only by overcoming the stringent response but also by increasing the synthesis of EF-Tu and MnSOD.

The outer membrane protein TolC from Sinorhizobium meliloti affects protein secretion, polysaccharide biosynthesis, antimicrobial resistance, and symbiosis

Sinorhizobium meliloti is capable of establishing a symbiotic nitrogen fixation relationship with Medicago sativa. During this process, it must cope with diverse environments and has evolved different types of transport systems that help its propagation in the plant roots. TolC protein family members are the outer-membrane components of several transport systems involved in the export of diverse molecules, playing an important role in bacterial survival. In this work, we have characterized the protein TolC from S. meliloti 2011. An insertional mutation in the tolC gene strongly affected the resistance phenotype to antimicrobial agents and induced higher susceptibility to osmotic and oxidative stresses. Immunodetection experiments and comparison of the extracellular proteins present in the supernatant of the wild-type versus tolC mutant strains showed that the calcium-binding protein ExpE1, the endoglycanase ExsH, and the product of open reading frame SMc04171, a putative hemolysin-type calcium-binding protein, are secreted by a TolC-dependent secretion system. In the absence of TolC, neither succinoglycan nor galactoglucan were detected in the culture supernatant. Moreover, S. meliloti tolC mutant induced a reduced number of nonfixing nitrogen nodules in M. sativa roots. Taken together, our results confirm the importance of TolC in protein secretion, exopolysaccharide biosynthesis, antimicrobials resistance, and symbiosis.

Optimization of kappa-carrageenase production by Pseudoalteromonas sp. AJ5

OBJECTIVES

To optimize the culture conditions of Pseudoalteromonas sp. AJ5 for a higher production of extracellular kappa-carrageenase.

METHODS

A kappa-carrageenan-degrading bacterium AJ5, capable of utilizing kappa-carrageenan as sole source of carbon and energy, was isolated from the intestine of holothurian Apostichopus japonicus by enrichment culture technique. The strain was identified as the genus Pseudoalteromonas sp. according to its morphological and physiological characterization and 16S rRNA gene analysis. Culture conditions for the bacterium were standardized for the maximal productivity of the extracellular kappa-carrageenase by the single factor and orthogonal tests.

RESULTS

According to the single factor test, the optimal culture conditions were: 75 mL medium in 250 mL Erlenmeyer flask, shaking speed of 150 r/min, inoculum's volume 7%, and pH 8.0. Based on the single factor and orthogonal tests the optimal medium components were: kappa-carrageenan (1 g/L), beef extract (2 g/L ), NaCl (20 g/L), K2HPO4.3H2O (1 g/L), MgSO4.7H2O (0.5 g/L), MnCl2.4H2O (0.2 g/L), FePO4.4H2O (0.01 g/L), with the incubation temperature and time of 28 degrees C and 28 h.

CONCLUSION

Pseudoalteromonas sp. AJ5 secreted an extracellular kappa-carrageenase. Under the optimal culture conditions, four-fold increase in kappa-carrageenase activity was achieved as compared to the control.

Structure of microvillar enzymes in different phases of their life cycles

Structural changes have been studied during the life cycles of three glycosidases: sucrase-isomaltase (EC 3.2.48-10), lactase-phlorizin hydrolase (EC 3.2.1.23-62), maltase-glucoamylase (EC 3.2.1.20); and three peptidases: aminopeptidase A (EC 3.4.11.7), aminopeptidase N (EC 3.4.11.2) and dipeptidyl peptidase IV (EC 3.4.14.5). The final forms of the enzymes can be divided into at least two groups: the sucrase-isomaltase type, characterized as dimers, which are asymmetric in their hydrophilic parts, have two types of active site and anchor only on one subunit; and the aminopeptidase N type, characterized as dimers, which are symmetric in their hydrophilic part, have only one type of active site and anchor on both subunits. These enzymes are likely to be synthesized on rough endoplasmic reticulum and simultaneously glycosylated into endoglycosidase H-sensitive forms. They are later reglycosylated to endoglycosidase H-resistant forms, which have relative molecular masses similar to the final forms. Enzymes of the sucrase-isomaltase type seem to be synthesized with a polypeptide-chain length corresponding to the sum of both subunits, whereas enzymes of the aminopeptidase N type seem to be synthesized with a polypeptide-chain length corresponding to the constituent subunits themselves. Not much is known about the catabolism of these enzymes. The enzyme activities and the amounts of enzyme protein decrease at the top of the villi, probably due to release into the lumen. The subunits of aminopeptidase N are cleaved by pancreatic proteases to smaller peptides, and sucrase-isomaltase may lose its sucrase polypeptide, while both enzymes remain bound to the membrane.

[Cancer chemopreventive agents: glucosinolates and their decomposition products in white cabbage (Brassica oleracea var. capitata)]

A number of recent epidemiological studies have indicated that high intake of white cabbage may be associated with a lower risk of neoplastic diseases such as cancer of the pancreas, breast, prostate, stomach, and lungs. The anticarcinogenic activity is related to the presence of biologically active components in this vegetable. The chemopreventive effects of cabbage may be connected with modulation of the activity of phase I and II detoxification enzymes and other mechanisms triggered by glucosinolates and products of their decomposition, which are formed as a result of hydrolysis catalyzed by the enzyme myrosinase. The products of glucosinolate decomposition influence a number of cellular processes through the regulation of transcription factor levels, signaling pathways, the cell cycle, and apoptosis. The beneficial activities and especially the chemopreventive effects of the compounds present in cabbage point to the necessity of formulating scientifically based dietary recommendations enabling the optimal exploitation of this vegetable in health protection.

High-level expression of a truncated 1,3-1,4-beta-D-glucanase from Fibrobacter succinogenes in Pichia pastoris by optimization of codons and fermentation

1,3-1,4-beta-D-glucanase is an important endoglycosidase in the brewing and animal feed industries. To achieve high-level expression of recombinant glucanase in Pichia pastoris, we designed sequences encoding the alpha-factor signal peptide from Saccharomyces cerevisiae and the truncated 1,3-1,4-beta-D-glucanase from Fibrobacter succinogenes as a whole. The codons encoding the 52 amino acids of the signal peptide and 106 residues of the glucanase protein were optimized for expression in P. pastoris; 189 nucleotides were changed. The G + C content was adjusted to 48-49%, and AT-rich stretches were eliminated to avoid premature termination. The messenger ribonucleic acid secondary structure near the AUG start codon was also adjusted to ensure efficient translation; the resulting glucanase production was twofold higher compared with that achieved with gene structure optimization alone. We also propose a new fermentation strategy for the induction phase, in which 5/95% glycerol/methanol mixed feed was used in days 1-3 and 100% methanol was used on days 4-6. By comparison with methanol feed and glycerol/methanol-mixed feed alone, the yield of recombinant glucanase increased by 38.5 and 16.5%, respectively. The expressed optimized recombinant 1,3-1,4-beta-D-glucanase constituted approximately 90% of the total secreted protein, reaching up to 3 g l(-1) in the medium.

A stress-induced rice (Oryza sativa L.) beta-glucosidase represents a new subfamily of glycosyl hydrolase family 5 containing a fascin-like domain

GH5BG, the cDNA for a stress-induced GH5 (glycosyl hydrolase family 5) beta-glucosidase, was cloned from rice (Oryza sativa L.) seedlings. The GH5BG cDNA encodes a 510-amino-acid precursor protein that comprises 19 amino acids of prepeptide and 491 amino acids of mature protein. The protein was predicted to be extracellular. The mature protein is a member of a plant-specific subgroup of the GH5 exoglucanase subfamily that contains two major domains, a beta-1,3-exoglucanase-like domain and a fascin-like domain that is not commonly found in plant enzymes. The GH5BG mRNA is highly expressed in the shoot during germination and in leaf sheaths of mature plants. The GH5BG was up-regulated in response to salt stress, submergence stress, methyl jasmonate and abscisic acid in rice seedlings. A GUS (glucuronidase) reporter tagged at the C-terminus of GH5BG was found to be secreted to the apoplast when expressed in onion (Allium cepa) cells. A thioredoxin fusion protein produced from the GH5BG cDNA in Escherichia coli hydrolysed various pNP (p-nitrophenyl) glycosides, including beta-D-glucoside, alpha-L-arabinoside, beta-D-fucoside, beta-D-galactoside, beta-D-xyloside and beta-D-cellobioside, as well as beta-(1,4)-linked glucose oligosaccharides and beta-(1,3)-linked disaccharide (laminaribiose). The catalytic efficiency (kcat/K(m)) for hydrolysis of beta-(1,4)-linked oligosaccharides by the enzyme remained constant as the DP (degree of polymerization) increased from 3 to 5. This substrate specificity is significantly different from fungal GH5 exoglucanases, such as the exo-beta-(1,3)-glucanase of the yeast Candida albicans, which may correlate with a marked reduction in a loop that makes up the active-site wall in the Candida enzyme.

Inulinase-producing marine yeasts: evaluation of their diversity and inulin hydrolysis by their crude enzymes

Total 427 yeast strains from seawater, sediments, mud of salterns, guts of the marine fish, and marine algae were obtained. After inulinase activity of the yeast cultures was estimated, we found that four strains (OUC1, G7a, OUC2, and G7a1) of the marine yeasts grown in the medium with inulin could secrete a large amount of inulinase into the medium. The results of routine identification and molecular methods show that they belong to Pichia guilliermondii OUC1, Cryptococcus aureus G7a, Yarrowia lipolytica OUC2, and Debaryomyces hansenii G7a1, respectively. The optimal pHs of inulinase activity produced by them were 6.0, 5.0, 5.0, and 5.0, respectively, while the optimal temperatures of inulinase activity produced by them were 60 degrees , 50 degrees , 60 degrees , and 50 degrees C, respectively. A large amount of monosaccharides and a trace amount of oligosaccharides were detected after the hydrolysis by the crude inulinase produced by P. guilliermondii OUC1, indicating that the crude inulinase had a high exoinulinase activity while a large amount of monosaccharides and oligosaccharides were detected after inulin hydrolysis by the crude inulinase produced both by C. aureus G7a and D. hansenii G7a1. However, no monosaccharides and disaccharides were detected after inulin hydrolysis by the crude inulinase produced by Y. lipolytica OUC2, suggesting that the crude inulinase had no exoinulinase activity.

Production of inulinase by Xanthomonas campestris pv phaseoli using onion (Allium cepa) and garlic (Allium sativum) peels in solid state cultivation

AIMS

To access inulinase production by Xanthomonas campestris pv phaseoli using the submerged and solid state cultivation (SSC) methods.

METHODS AND RESULTS

Various carbon sources, inulin-rich solid substrates and pure synthetic inulin were tested for their efficiency in inulinase induction. The highest inulinase production (17.42 IU ml(-1)) in submerged cultures of X. campestris was observed with inulin as a carbon source with an initial pH, temperature and agitation of 7.0, 37 degrees C and 150 rev min(-1) respectively. Among the various substrates, garlic peels (117 IU gds(-1)) and onion peels (101 IU gds(-1)) were found to be the best for inulinase production.

CONCLUSION

The inulinase production level of X. campestris was 6.7-fold higher in garlic and 5.8-fold in onion, under optimized SSC conditions compared with the submerged culture.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report on inulinase production from garlic and onion peels by X. campestris using SSC. SSC is an efficient method for inulinase production by X. campestris for commercial applications.

Production of inulinase by solid-state fermentation: effect of process parameters on production and preliminary characterization of enzyme preparations

This work was aimed at producing inulinase by solid-state fermentation of sugarcane bagasse, using factorial design to identify the effect of corn steep liquor (CSL) and soybean bran concentration, particle size of bagasse and size of inoculum. Maximum inulinase activity achieved was 250 U per g of dry substrate (gds) at 20% (w/w) of CSL, 5% (w/w) of soybean bran, 1 x 10(10) cells mL(-1) and particle size of bagasse in the range 9/32 mesh. The use of soybean bran decreased the time to reach maximum activity from 96 to 24 h and the maximum productivity achieved was 8.87 U gds(-1) h(-1). The maximum activity was obtained at pH 5.0 and 55.0 degrees C. Within the investigated range, the enzyme extract was more thermostable at 50.0 degrees C, showing a D-value of 123.1 h and deactivation energy of 343.9 kJ gmol(-1). The extract showed highest stability from pH 4.5 to 4.8. Apparent K(m) and V(max) are 7.1 mM and 17.79 M min(-1), respectively.

Optimization of medium and process parameters for the production of inulinase from a newly isolated Kluyveromyces marxianus YS-1

A newly isolated strain of Kluyveromyces marxianus YS-1 was used for the production of extra cellular inulinase in a medium containing inulin, meat extract, CaCl2 and sodium dodecyl sulphate (SDS). Fermentation medium pH 6.5, cultivation temperature 30 degrees C and 5% (v/v) inoculum of 12 h-old culture were optimal for enzyme production (30.8 IU/ml) with a fermentation time of 72 h at shake flask level. Raw inulin (2%, w/v) extracted from dahlia tubers by processing at 15 kg/cm2 for 10 min was optimum for bioreactor studies. Maximum enzyme production (55.4 IU/ml) was obtained at an agitation rate of 200 rpm and aeration of 0.75 vvm in a stirred tank reactor with a fermentation time of 60 h.

Evaluation of arabinofuranosidase and xylanase activities of Geobacillus spp. isolated from some hot springs in Turkey

Some hot springs located in the west of Turkey were investigated with respect to the presence of thermophilic microorganisms. Based on phenotyping characteristics and 16S rRNA gene sequence analysis, 16 of the isolates belonged to the genus Geobacillus and grew optimally at about 60 degrees C on nutrient agar. 16S rRNA gene sequence analysis showed that these isolates resembled Geobacillus species by > or = 97%, but SDS-PAGE profiles of these 16 isolates differ from some of the other species of the genus Geobacillus. However, it is also known that analysis of 16S rRNA gene sequences may be insufficient to distinguish between some species. It is proposed that recN sequence comparisons could accurately measure genome similarities for the Geobacillus genus. Based on recN sequence analysis, isolates 11, IT3, and 12 are strains of G stearothermophilus; isolate 14.3 is a strain of G thermodenitrificans; isolates 9.1, IT4.1, and 4.5 are uncertain and it is required to make further analysis. The presence of xylanase and arabinofuranosidase activities, and their optimum temperature and pH were also investigated. These results showed that 7 of the strains have both xylanase and arabinofuranosidase activities, 4 of them has only xylanase, and the remaning 5 strains have neither of these activities. The isolates 9.1, 7.1, and 3.3 have the highest temperature optima (80 degrees C), and 7.2, 9.1, AO4, 9.2, and AO17 have the highest pH optima (pH 8) of xylanase. Isolates 7.2, AO4, AC15, and 12 have optimum arabinofuranosidase activities at 75 degrees C, and only isolate AC 15 has the lowest pH of 5.5.

[Induction of synthesis and activation of Penicillium commune alpha-L-rhamnosidase]

For the first time the influence of a number of synthetic porfirin and fluoren derivatives, coordinative germanium substances and surfactants on the biosynthesis and activity of Penicillium commune 266 alpha-L-rhamnosidase has been studied. It is shown that some of porfirin derivatives and coordinative germanium substances may be used as inducers of biosynthesis (143-430%) and also as stimulators of alpha-L-rhamnosidase activity (15-44%). It is more expedient to use biscitratgermanium acid in a complex with asparaginic acid (430%) or threonine (370%) as inducers of biosynthesis of enzyme. At the same time the use of porfirin derivatives, in particular meso-tetra(N-methyl-6-chinoline)porfirin tosilate or its manganese complex, is more efficient as stimulators (40%) of alpha-L-rhamnosidase activity. The utilization of such surfactants as tregaloso-, peptido- and rhamnolipids is not expedient. These compounds either do not influence or inhibit biosynthesis and activity of P. commune alpha-L-rhamnosidase. Only in concentration of 0.01% rhamnolipid increased the activity of enzyme by 7.5%.

Functional characterization and evolutionary implication of the internal 157-amino-acid sequence of an exoinulinase from Penicillium sp. strain TN-88

An extracellular exoinulinase from the filamentous fungus Penicillium sp. strain TN-88 has a 14-fold higher specific activity of 743 U/mg toward inulin than its equivalent from the Aspergillus niger strain 12 and possesses an internal 157-amino-acid sequence whose corresponding region is absent in the A. niger enzyme. On the basis of sequence alignment, the internal region D' encoding the 157-amino-acid sequence in the Penicillium exoinulinase gene inuD cDNA was inserted into the site between the nucleotides 897 and 898 of the A. niger exoinulinase gene inuE cDNA. The resultant inuE::D' fusion was expressed in the methylotrophic yeast Pichia pastoris. The K(m) value of the secreted hybrid enzyme InuE::D' for inulin hydrolysis was about 1/15 that of the A. niger InuE, whereas its k(cat) value did not differ greatly from that of the InuE. These observations indicate that the Penicillium exoinulinase has evolved by the horizontal transfer and integration of a relevant DNA segment and that the internal sequence D' functions as an additional noncatalytic inulin-affinity region.

Substrate induction and statistical optimization for the production of chitosanase from Microbacterium sp. OU01

The chitosanase production was markedly enhanced by substrate induction, statistical optimization of medium composition and culture conditions by Microbacterium sp. OU01 in shake-flask. A significant influence of (NH(4))(2)SO(4), MgSO(4).7H(2)O and initial pH on chitosanase production was noted with Plackett-Burman design. It was then revealed with the method of steepest ascent and response surface methodology (RSM) that 19.0g/L (NH(4))(2)SO(4), 1.3g/L MgSO(4) and an initial pH of 2.0 were optimum for the production of chitosanase; colloidal chitosan appeared to be the best inducer for chitosanase production by Microbacterium sp. OU01. This optimization strategy led to the enhancement of chitosanase from 3.6U/mL to 118U/mL.

[The influence of coordinational germanium compounds on the activity of glycosidases]

The ability of the synthesized compounds of germanium with bioligands to affect the biosynthesis and activity of alpha-amylase and alpha-L-rhamnosidase has been studied. It was established the most complexes tested induced biosyntheis of alpha-amylase of Bacillus subtilis 147 (119-252%) with the exception of Pam (Pyracetam) and II (Ge-nicotinic-citric acid). At the same time the biosynthesis of alpha-amylase of Bacillus licheniformis 234 and alpha-L-rhamnosidase of Penicillium commune was inhibited by a number of synthesized compounds. The complexes IV (Ge-malonic acid) and VIII (Ge-nicotinamide-malonic acid) did not exert any effect on the biosynthesis of alpha-amylase however complex IV stimulated alpha-L-rhamnosidase biosynthesis on the 3rd day of producer cultivation. The study of influence of the studied germanium compounds on the activity of alpha-amylase and alpha-L-rhamnosidase gives every reason to suppose that they are the inhibitors of the above-mentioned enzymes.

Recombinant expression and characterization of XynD from Bacillus subtilis subsp. subtilis ATCC 6051: a GH 43 arabinoxylan arabinofuranohydrolase

The complete genome sequence of Bacillus subtilis reveals that sequences encoding several hemicellulases are co-localised with a gene (xynD) encoding a putative family 43 glycoside hydrolase that has not yet been characterised. In this work, xynD has been isolated from genomic DNA of B. subtilis subsp. subtilis ATCC 6051 and cloned for cytoplasmatic expression in Escherichia coli. Recombinant XynD (rXynD) was purified using ion-exchange chromatography and gel permeation chromatography. The enzyme had a molecular mass of approximately 52 kDa, a pI above 9.0 and releases alpha-L-arabinose from arabinoxylo-oligosaccharides as well as arabinoxylan polymers with varying degree of substitution. Using para-nitrophenyl-alpha-L-arabinofuranoside as substrate, maximum activity was observed at pH 5.6 and 45 degrees C. The enzyme retained its activity over a large pH range, while activity was lost after pre-incubation above 50 degrees C. Gas-liquid chromatography and proton nuclear magnetic resonance spectrometry analysis indicated that rXynD specifically releases arabinofuranosyl groups from mono-substituted C-(O)-2 and C-(O)-3 xylopyranosyl residues on the xylan backbone. As rXynD did not display endoxylanase, xylosidase or arabinanase activity and was inactive on arabinan, we conclude that this enzyme is best described as an arabinoxylan arabinofuranohydrolase.

Co-expression of the Thermotoga neapolitana aglB gene with an upstream 3'-coding fragment of the malG gene improves enzymatic characteristics of recombinant AglB cyclomaltodextrinase

A cluster of Thermotoga neapolitana genes participating in starch degradation includes the malG gene of sugar transport protein and the aglB gene of cyclomaltodextrinase. The start and stop codons of these genes share a common overlapping sequence, aTGAtg. Here, we compared properties of expression products of three different constructs with aglB from T. neapolitana. The first expression vector contained the aglB gene linked to an upstream 90-bp 3'-terminal region of the malG gene with the stop codon overlapping with the start codon of aglB. The second construct included the isolated coding sequence of aglB with two tandem potential start codons. The expression product of this construct in Escherichia coli had two tandem Met residues at its N terminus and was characterized by low thermostability and high tendency to aggregate. In contrast, co-expression of aglB and the 3'-terminal region of malG (the first construct) resulted in AglB with only one N-terminal Met residue and a much higher specific activity of cyclomaltodextrinase. Moreover, the enzyme expressed by such a construct was more thermostable and less prone to aggregation. The third construct was the same as the second one except that it contained only one ATG start codon. The product of its expression had kinetic and other properties similar to those of the enzyme with only one N-terminal Met residue.

Substrate and product hydrolysis specificity in family 11 glycoside hydrolases: an analysis of Penicillium funiculosum and Penicillium griseofulvum xylanases

Two genes encoding family 11 endo-(1,4)-beta-xylanases from Penicillium griseofulvum (PgXynA) and Penicillium funiculosum (PfXynC) were heterologously expressed in Escherichia coli as glutathione S-transferase fusion proteins, and the recombinant enzymes were purified after affinity chromatography and proteolysis. PgXynA and PfXynC were identical to their native counterparts in terms of molecular mass, pI, N-terminal sequence, optimum pH, and enzymatic activity towards arabinoxylan. Further investigation of the rate and pattern of hydrolysis of PgXynA and PfXynC on wheat soluble arabinoxylan showed the predominant production of xylotriose and xylobiose as end products. The initial rate data from the hydrolysis of short xylo-oligosaccharides indicated that the catalytic efficiency increased with increasing chain length (n) of oligomer up to n = 6, suggesting that the specificity region of both Penicillium xylanases spans about six xylose units. In contrast to PfXynC, PgXynA was found insensitive to the wheat xylanase inhibitor protein XIP-I.

Induction of pullulanase production in Bacillus cereus FDTA-13

Studies were carried out on the production of pullulanase by a newly isolated strain Bacillus cereus FDTA-13. High titres of the enzyme were obtained in a medium containing branched polysaccharides. To further enhance the yield, induction of pullulanase using conventional inducers were studied. Maltooligosaccharides (maltose to maltotetraose) when added in the medium individually, or in a 1:1 combination of maltotriose and maltotetraose resulted different levels of pullulanase compared to control. Growth under carbon limited conditions (5 g l(-1)) with inducers resulted remarkably enhanced pullulanase activity. Pullulanase activity was severely repressed in presence of glucose. Low levels of pullulanase was observed in nitrogen limited medium, even with combinations of several maltosaccharides.

Glycosyl hydrolases of cell wall are induced by sugar starvation in Arabidopsis

Three Arabidopsis genes encoding a putative beta-galactosidase (At5g56870), beta-xylosidase (At5g49360) and beta-glucosidase (At3g60140) are induced by sugar starvation. The deduced proteins belong to the glycosyl hydrolase families 35, 3 and 1, respectively. They are predicted to be secretory proteins that play roles in modification of cell wall polysaccharides based on amino acid similarity. The beta-galactosidase encoded by At5g56870 was identified as a secretory protein in culture medium of suspension cells by mass spectrometry analysis. This protein was specifically detected under sugar-starved conditions with a specific antibody. Induction of these genes was repressed in suspension cells grown with galactose, xylose and glucose, as well as with sucrose. In planta, expression of the genes and protein accumulation were detected when photosynthesis was inhibited. Glycosyl hydrolase activity against galactan also increased during sugar starvation. The amount of monosaccharide in pectin and hemicellulose in detached leaves decreased in response to sugar starvation. These findings suggest that the cell wall may function as a storage reserve of carbon in addition to providing physical support for the plant body.

Paenibacillus strain MP-1: a new source of mutanase

A mutan-degrading bacterium, closely related to Paenibacillus curdlanolyticus, was isolated from soil. It produced 0.4 U mutanase ml(-1 )in 2 days in shake-flask cultures when bacterial mutan was the sole carbon source. Mutanase activity was optimal at pH 6.2 and 45 degrees C over 1 h and was stable between pH 5.8 and 12 at 4 degrees C for 24 h and up to 40 degrees C for 1 h. Mutan produced by Streptococcus mutans was rapidly hydrolyzed by this enzyme. The hydrolysis of mutan (1 g l(-1)) resulted in 17% saccharification over 2 h and, at the same time, glucan was entirely solubilized.

In vivo selection for the enhancement of Thermotoga maritima exopolygalacturonase activity at neutral pH and low temperature

The aim of this study was to develop an Escherichia coli-based metabolic selection system for the uncovering of new oligogalacturonate-active enzymes. Based on the expression of the specific permease TogMNAB, this system enabled the entry of oligogalacturonates into the cytoplasm of E. coli thus providing a modified strain usable for this purpose. This tool was used for the metabolic selection of Thermotoga maritima exopolygalacturonase (TmGalU) mutants enabling the uptake of sodium trigalacturonate as the sole carbon source by the bacterium. In only one round of error-prone PCR and selection, mutants of TmGalU with a 4-fold increased turnover at pH 7.0 and 2-fold more active at 37 degrees C than wild-type enzyme were isolated. These results show the versatility of this strain for the evolution of oligogalacturonate-active enzymes.

Inulinase production by a marine yeast Pichia guilliermondii and inulin hydrolysis by the crude inulinase

Marine yeast strain 1, isolated from the surface of a marine alga, was found to secrete a large amount of inulinase into the medium. This marine yeast was identified as a strain of Pichia guilliermondii according to the results of routine yeast identification and molecular methods. The crude inulinase produced by this marine yeast worked optimally at pH 6.0 and 60 degrees C. The optimal medium for inulinase production was seawater containing 4.0% (w/v) inulin and 0.5% (w/v) yeast extract, while the optimal cultivation conditions for inulinase production were pH 8.0, 28 degrees C and 170 rpm. Under the optimal conditions, over 60 U ml(-1) of inulinase activity was produced within 48 h of fermentation in shake flasks. A large amount of monosaccharides and a trace amount of oligosaccharides were detected after the hydrolysis, indicating that the crude inulinase had a high exoinulinase activity.

[Optimization of cultivation conditions of Penicillium palitans strain 266 which synthesizes alpha-L-rhamnosidase]

The influence of different factors on the biosynthesis of extracellular alpha-L-rhamnosidase in Penicillium palitans at submerged cultivation has been investigated. It was shown that rhamnose and NaNO3 are the optimum carbon and nitrogen sources, respectively. The temperature of 26 degrees C, pH 5.0, growing in 50 ml of the medium at swing velocity 160 rev/min, adding of 5% of inoculum with cultivation for 4 days are the optimal parameters.