Cloning of an Aspergillus niger invertase gene by expression in Trichoderma reesei

The filamentous fungus Aspergillus niger produces two glycosylated forms of the sucrose-hydrolysing enzyme, invertase. In contrast, some Trichoderma species lack invertase and are unable to utilise sucrose as a sole carbon source. Using an A. niger genomic library constructed in a cosmid vector containing the ura5 gene of Podospora anserina as a selectable marker, and the T. reesei ura5- strain as a sucrose-minus recipient strain, an A. niger invertase gene (suc1) has been cloned by a sib selection procedure. PAGE and enzyme analysis confirmed that transformants had acquired invertase activity. The cloned gene contained DNA sequences which were complementary to the amino-acid sequences of tryptic peptides found in invertase purified from A. niger. The suc1 invertase gene can be used as a dominant selectable marker for the transformation of Trichoderma strains.

Glycoprotein biosynthesis in the alg3 Saccharomyces cerevisiae mutant. I. Role of glucose in the initial glycosylation of invertase in the endoplasmic reticulum

Oligosaccharides on invertase restricted to the endoplasmic reticulum (ER) in alg3,sec18 yeast at 37 degrees C were found to be 20% wild type Man8GlcNAc and 80% Man1 alpha-->2Man1 alpha-->2Man1 alpha-->3(Man1 alpha-->6)Man1 beta-->4GlcNAc2 (Verostek, M.F., Atkinson, P.H., and Trimble, R. B. (1991) J. Biol. Chem. 266, 5547-5551). These results suggested that alg3 was slightly leaky, but did not address whether the oligosaccharide-lipid Man9GlcNAc2 and Man5GlcNAc2 precursors were glucosylated in alg3 yeast. Therefore, an alg3,sec18,gls1 strain was constructed to delete the GLS1-encoded glucosidase I responsible for trimming the terminal alpha 1,2-linked glucose from newly transferred Glc3ManxGlcNAc2 oligosaccharides. Invertase activity was overexpressed 5-10-fold on transforming this strain with a multicopy plasmid (pRB58) carrying the SUC2 gene, and preparative amounts of the ER form of external invertase, derepressed and accumulated at 37 degrees C, were purified. The N-linked glycans were released by sequential treatment with endo-beta-N-acetylglucosaminidase H (endo H) and peptide-N4-N-acetyl-beta-glucosaminyl asparagine amidase. Oligosaccharide pools were sized separately on Bio-Gel P-4, which showed that endo H released about 17% of the carbohydrate as Glc3Man8GlcNAc, while peptide-N4-N-acetyl-beta-glucosaminyl asparagine amidase released the remainder as Hex8GlcNAc2 and Man5GlcNAc2 in a 1:4 ratio. Glycan structures were assigned by 500-MHz two-dimensional DQF-COSY 1H NMR spectroscopy, which revealed that the endo H-resistant Hex8GlcNAc2 pool contained Glc3Man5GlcNAc2 and Man8GlcNAc2 in a 6:4 ratio, the latter a different isomer from that formed by the ER alpha 1,2-mannosidase (Byrd, J. C., Tarentino, A. L., Maley, F., Atkinson, P. H., and Trimble, R. B. (1982) J. Biol. Chem. 257, 14657-14666). Recovery of Glc3Man8GlcNAc and not the ER form of Man8GlcNAc provided an internal control indicating the absence of glucosidase I, which was confirmed by incubation of [3H]Glc3[14C]Man9GlcNAc with solubilized membranes from either alg3,sec18,gls1 or alg3,sec18,GLS1 strains. Chromatographic analysis of the products showed that [3H]Glc was removed only in the presence of the GLS1 gene product. Thus, the vast majority of the N-linked glycosylation in the ER of alg3 yeast (> 75%) occurs by transfer of Man5GlcNAc2 without prior addition of the 3 glucoses normally found on the lipid-linked precursor.

Glycoprotein biosynthesis in the alg3 Saccharomyces cerevisiae mutant. II. Structure of novel Man6-10GlcNAc2 processing intermediates on secreted invertase

Alg3 yeast mutants synthesize endoglycosidase H-resistant oligosaccharides whose precursor for elongation is Man1 alpha-->2Man1 alpha-->2Man1 alpha-->3(Man1 alpha-->6)Man1 beta-->4GlcNAc2 (Verostek, M.F., Atkinson, P.H., and Trimble, R. B. (1991) J. Biol. Chem. 266, 5547-5551). To characterize alg3 glycan elongation in vivo, oligosaccharides on alg3,sec18 invertase synthesized and secreted at 26 degrees C were released with peptide-N4-N-acetyl-beta-glucosaminyl asparagine amidase and purified by Bio-Gel P-4 chromatography. Large (Man > 30GlcNAc2) and intermediate (Man5-10GlcNAc2) sized oligosaccharides were pooled separately, and the smaller ones were exchanged with 2H2O for one- and two-dimensional DQF-COSY 1H NMR analyses at 500 MHz. Although there was no detectable substitution of the terminal alpha 1,6-core-linked mannose, addition of alpha 1,6-, alpha 1,2-, and alpha 1,3-mannoses to the alpha 1,3-linked core branch of a majority of the Man5 precursor was analogous to core-filling reactions seen on wild type invertase glycans (Trimble, R.B., and Atkinson, P.H. (1986) J. Biol. Chem. 261, 9815-9824). Two additional types of oligosaccharide structures were found; those which retained glucose and those consistent with mannan elongation. Glucose retention appeared to be due to inefficient trimming from minor glucosylated intermediates, while mannan elongation was by extension of a new alpha 1,6-linked branch from the alpha 1,3-core-linked residue as seen in wild-type core oligosaccharides (Hernandez, L.M., Ballou, L., Alvarado, E., Gillece-Castro, B.L., Burlingame, A.L., and Ballou, C. E. (1989) J. Biol. Chem. 264, 11849-11856) or mnn1,mnn2,mnn10 processing intermediates (Ballou, L., Alvarado, E., Tsai, P-k., Dell, A., and Ballou, C.E. (1989) J. Biol. Chem. 264, 11857-11864). Thus, the alpha 1,6-linked branch additions which form Man9GlcNAc2-PP-dolichol from Man5GlcNAc2-PP-dolichol appear to provide important structural information enabling efficient recognition by the endoplasmic reticulum-glucosyltransferases forming oligosaccharide-lipid as well as the glucosidases involved in early trimming reactions, but the alg3 mutant documents that they are unnecessary for normal yeast mannan elongation.

Physiological studies on xylanase production by Penicillium funiculosum on some agricultural wastes

Studies were carried out on production of Xylanase enzyme from P. funiculosum NRCE-629 using a number of alkali-treated lignocellulosic wastes as carbon and energy sources as compared to pure xylan polymer. Sugar cane bagasse, rice straw and wheat straw yielded enzyme levels higher than that obtained on pure xylan. Physiological studies on enzyme formation using those three agricultural wastes revealed that optimum enzyme yields are obtained in media containing 2% substrate concentration. The enzyme synthesis was favored in agitated cultures with an air:medium ratio corresponding to 3:2 respectively with inoculum size of 10% (v/v). Further studies using rice straw medium yielded highest enzyme level after five days of aerobic growth at 30 degrees C with initial pH of medium adjusted to 5.0. Results are discussed in the light of possible application.

Overexpression of the Bacillus subtilis and circulans xylanases in Escherichia coli

An efficient expression system for a low-molecular mass xylanase in Escherichia coli has been developed. A gene encoding the mature Bacillus circulans (Bc) xylanase was designed to imitate the frequency of degenerate codons used in E. coli. Appropriate degenerate codons were used to create multiple unique restriction sites for future mutagenesis studies. The synthetic gene was constructed in two stages, both involving ligation of overlapping oligonucleotides. The synthetic Bc gene was then converted to a Bacillus subtilis (Bs) xylanase gene via a single codon substitution (Thr147Ser). The plasmids containing both synthetic genes were further modified for the direct expression in E. coli. Under the control of the lac promoter, recombinant xylanase has been produced at levels as high as 300 mg/liter in soluble form in the cytoplasm. This efficiency represented a dramatic improvement over all previous attempts involving the expression of the natural genes, with the xylanase being secreted in those cases. Characterization of our gene products indicated that the purified recombinant product was correctly processed and enzymatically active.

Effects of GAL10-SUC2 promoter combinations on SUC2 gene expression in S. cerevisiae

The plasmid series YEP51 delta n bearing GAL10-SUC2 promoter combinations were constructed by inserting SUC2 gene with different upstream deletions downstream GAL10 promoter on YEP51. After transforming yeast cells S. cerevisiae, the invertases expressed by each of the transformants were measured and analysed by means of PAGE. The results showed that: 1) The SUC2 gene with upstream deletion to at -636bp expressed high level glycosylated form of invertase under glucose derepression, while SUC2 gene with more extensive deletions to -223 bp or more lost its response to glucose derepression; 2) Each part of GAL10-SUC2 promoter combination acted almost independently. All of the combinations showed no apparent coordinated promoter function under our experimental conditions; 3) Sequences between -89bp and -41bp of SUC2 upstream region are responsible for constitutive expression of nonglycosylated invertase. The two tracts of poly (dA-dT) of this region may serve as promoter elements.

Duplication of secretion signal sequences is deleterious for the secretion of human interferon alpha 4 from Saccharomyces cerevisiae and Bacillus subtilis

Tandem duplication of a mitochondrial import leader sequence has been shown to markedly increase the efficiency of translocation of chimaeric precursors across mitochondrial membranes to the mitochondrial matrix. The principle of leader sequence duplication was applied to the protein secretion system of the yeast Saccharomyces cerevisiae and of Bacillus subtilis. The secretion signal sequences of yeast invertase and B. subtilis neutral protease were used to direct the secretion of human interferon alpha 4. Our results show that the duplication of these N-terminal signal sequences does not enhance secretion of interferon alpha 4 in either of the cell systems studied.

A bifunctional enzyme, with separate xylanase and beta(1,3-1,4)-glucanase domains, encoded by the xynD gene of Ruminococcus flavefaciens

Adjacent regions of a Ruminococcus flavefaciens 17 DNA fragment were found to encode xylanase and beta(1,3-1,4)-glucanase activities. Sequencing of this fragment showed that both activities are encoded by a single 2,406-bp open reading frame corresponding to the xynD gene. The predicted product has a characteristic signal sequence that is followed by an amino-terminal domain related to family G xylanases, while the carboxyterminal domain is related to beta(1,3-1,4)-glucanases from several other bacterial species. These two domains are connected by a region of unknown function that consists of 309 amino acids and includes a 30-amino-acid threonine-rich sequence. A polypeptide having a molecular weight of approximately 90,000 and exhibiting xylanase and beta(1,3-1,4)-glucanase activities was detected in Escherichia coli cells carrying the cloned xynD gene. This is one of the first cases in which a microbial polysaccharidase has been shown to carry separate catalytic domains active against different plant cell wall polysaccharides within the same polypeptide. xynD is one of a family of related genes in R. flavefaciens that encode enzymes having multiple catalytic domains, and the amino terminus of XYLD exhibits a high degree of similarity with the corresponding regions of another xylanase, XYLA, which carries two different xylanase catalytic domains.

Molecular cloning of a gene involved in glucose sensing in the yeast Saccharomyces cerevisiae

Cells of the yeast Saccharomyces cerevisiae display a wide range of glucose-induced regulatory phenomena, including glucose-induced activation of the RAS-adenylate cyclase pathway and phosphatidylinositol turnover, rapid post-translational effects on the activity of different enzymes as well as long-term effects at the transcriptional level. A gene called GGS1 (for General Glucose Sensor) that is apparently required for the glucose-induced regulatory effects and several ggs1 alleles (fdp1, byp1 and cif1) has been cloned and characterized. A GGS1 homologue is present in Methanobacterium thermoautotrophicum. Yeast ggs1 mutants are unable to grow on glucose or related readily fermentable sugars, apparently owing to unrestricted influx of sugar into glycolysis, resulting in its rapid deregulation. Levels of intracellular free glucose and metabolites measured over a period of a few minutes after addition of glucose to cells of a ggs1 delta strain are consistent with our previous suggestion of a functional interaction between a sugar transporter, a sugar kinase and the GGS1 gene product. Such a glucose-sensing system might both restrict the influx of glucose and activate several signal transduction pathways, leading to the wide range of glucose-induced regulatory phenomena. Deregulation of these pathways in ggs1 mutants might explain phenotypic defects observed in the absence of glucose, e.g. the inability of ggs1 diploids to sporulate.

Molecular characterization of a fructanase produced by Bacteroides fragilis BF-1

The Bacteroides fragilis BF-1 fructanase-encoding gene (fruA) was cloned and expressed in Escherichia coli from the recombinant plasmid pBS100. The fruA gene consisted of 1,866 bp encoding a protein of 622 amino acids with a calculated M(r) of 70,286. The apparent M(r) of the fructanase, determined by in vitro cell-free transcription-translation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, was approximately 71,500. An alignment of the amino acid sequences of the B. fragilis BF-1 fructanase and the Bacillus subtilis levanase revealed that 45.5% of the amino acids were identical. The fruA gene was expressed in E. coli from its own promoter; however, no E. coli promoter-like sequence was evident upstream from the gene. A major E. coli transcription start point and a single B. fragilis BF-1 transcription start point were located. Expression of the fruA gene was constitutive in E. coli(pBS100) and B. fragilis BF-1. The ratio of sucrase activity to inulinase activity (S/I ratio) was constant for enzyme preparations from E. coli (pBS100), indicating that both activities were associated with the fructanase. For B. fragilis BF-1, the S/I ratio varied considerably depending on the carbon source used for growth, suggesting that a separate sucrase is produced in addition to the fructanase in B. fragilis BF-1. Localization experiments and TnphoA mutagenesis indicated that the fructanase was exported to the periplasm. Sequence analysis of the N-terminal region of the fructanase revealed a putative 30-amino-acid signal peptide. The enzymatic properties of the purified fructanase were investigated. The enzyme was able to hydrolyze sucrose, raffinose, inulin, and levan but not melezitose, indicating that it was a beta-D-fructofuranosidase which was able to hydrolyze beta(2-->6)-linked fructans.

Cloning and sequence analysis of the cyclomaltodextrinase gene from Bacillus sphaericus and expression in Escherichia coli cells

The gene for cyclomaltodextrinase (CDase; EC 3.2.1.54) from Bacillus sphaericus E-244 was cloned in the recombinant plasmid pCD629. Sequencing a portion of pCD629 revealed a unique open reading frame of 1,773 nucleotides coding for a 591-amino-acid polypeptide. The deduced polypeptide sequence showed about 50% homology with that of a neopullulanase, and was slightly homologous to those of the cyclodextrin glucanotransferases and the alpha-amylases. The optimum pH, specific activity and Km value for beta-cyclodextrin of the CDase that has been produced in Escherichia coli cells were 8.0, 16.4 units/mg protein, and 0.41 mM, respectively. These values were almost identical to those from B. sphaericus E-244.

Sugar uptake and involved enzymatic activities by yeasts and lactic acid bacteria: their relationship with breadmaking quality

The uptake kinetics of sugars present in wheat doughs and alpha-glucosidase as well as beta-fructosidase activities were determined in different strains of yeasts and lactic acid bacteria. These strains were previously selected according to their breadmaking quality. Saccharomyces cerevisiae (P6), Candida guilliermondii (P40), Lactobacillus plantarum (B31 and La18) and L. brevis (B21) showed good performance, while Sacch. fructuum (P43), L. cellobiosus (B37) and Enterococcus faecium (B11) yielded bread of lower quality. Leuconostoc mesenteroides (B10), when used in combination with other strains led also to high quality starters. All yeast strains used assimilated glucose, fructose and maltose, exhibiting saturable kinetics. Lactic acid bacteria showed saturable kinetics only for hexoses, whereas disaccharide uptake was linear. Sacch. cerevisiae, Leuconostoc mesenteroides, L. brevis and L. plantarum (B31) displayed better sugar uptake properties. For all the strains used alpha-glucosidase and beta-fructosidase activities were detected. The highest specific activities were found for Sacch. cerevisiae, C. guilliermondii and L. plantarum (B31). These results indicate good correlation between the parameters evaluated and the breadmaking potential of the microorganisms.

Cloning and extracellular expression in Escherichia coli of xylanases from an alkaliphilic thermophilic Bacillus sp. NCIM 59

A genomic DNA library of an alkaliphilic thermophilic Bacillus was constructed in Escherichia coli with pUC 8 vector and was screened using a Congo red xylan plate clearance assay. Six xylanase positive transformants having identical inserts showed immunological reactivity towards polyclonal antibodies raised against purified xylanase (M(r) 15,800) from the Bacillus. A 4.5-kb HindIII-EcoRI subfragment was found to code for two xylanases of M(r) 14,500 and 35,000. Equivalent amounts of xylanase activity were detected from IPTG induced and noninduced recombinants irrespective of the orientation of the 4.5-kb insert with respect to the lac promoter, indicating that xylanase gene expression was under the control of its own promoter. 95% of the xylanase activity (2 U/ml) was found in the extracellular culture filtrate. The hydrolysis of xylan by the recombinant xylanases yielded mainly xylobiose.

Cloning of the cyclomaltodextrinase gene from Bacillus subtilis high-temperature growth transformant H-17

The cyclomaltodextrinase gene from Bacillus subtilis high-temperature growth transformant H-17 was cloned on separate PstI, BamHI, and EcoRI fragments into the plasmid vector pUC18, but was expressed in an inactive form in the host, Escherichia coli DH5 alpha. High level constitutive expression of the gene product was also detrimental to the E. coli host, which led to structural instability of the recombinant plasmid. The cyclomaltodextrinase gene was cloned on a 3-kb EcoRI fragment into the plasmid vector pPL708, and the fragment was structurally maintained in the host B. subtilis YB886. The cloned gene product was synthesized in an enzymatically active form in the B. subtilis host; however, expression was at a low level. Subcloning of the 3-kb EcoRI fragment into pUC18 and transformation into E. coli XL1-Blue (F' lacIq) indicated that the cyclomaltodextrinase gene was cloned with its own promoter, since expression of the gene occurred in the absence of IPTG. Subcloning of the cyclomaltodextrinase gene downstream from the Bacillus temperature phage SPO2 promoter of pPL708 may increase expression of this gene.

Intercellular localization of acid invertase in tomato fruit and molecular cloning of a cDNA for the enzyme

The localization of acid invertase (AI, EC 3.2.1.26) in tomato fruits was studied. AI was localized in the intercellular fraction (cell wall fraction). A cDNA encoding a wall-bound form of AI from tomato fruits was cloned and its nucleotide sequence was determined. The cloned cDNA was 2363 base pairs long and contained an open reading frame of 1908 base pairs which encoded a polypeptide of 636 amino acids. RNA blot analysis indicated that the mRNA for the acid invertase was about 2.5 kb in length. The levels of the mRNA were low at the mature green stage but increased during ripening of fruit.

Production of high concentrations of ethanol from inulin by simultaneous saccharification and fermentation using Aspergillus niger and Saccharomyces cerevisiae

Pure nonhydrolyzed inulin was directly converted to ethanol in a simultaneous saccharification and fermentation process. An inulinase-hyperproducing mutant, Aspergillus niger 817, was grown in a submerged culture at 30 degrees C for 5 days. The inulin-digestive liquid culture (150 ml) was supplemented with 45 g of inulin, 0.45 g of (NH4)2SO4, and 0.15 g of KH2PO4. The medium (pH 5.0) was inoculated with an ethanol-tolerant strain, Saccharomyces cerevisiae 1200, and fermentation was conducted at 30 degrees C. An additional 20 g of inulin was added to the culture after 15 h of fermentation. S. cerevisiae 1200 utilized 99% of the 65 g of inulin during the fermentation, and produced 20.4 and 21.0% (vol/vol) ethanol from chicory and dahlia inulins, respectively, within 3 days of fermentation. The maximum volumetric productivities of ethanol were 6.2 and 6.0 g/liter/h for chicory and dahlia inulins, respectively. The conversion efficiency of inulin to ethanol was 83 to 84% of the theoretical ethanol yield.

[Genetic manipulation of the synthesis of fungal enzymes for use in the food industry]

Food industries use a great variety of enzymes as additives. The main percentage of them are produced by species of filamentous fungi. In this review we present the strategies to purify and overproduce this kind of enzymes using recombinant DNA techniques.

Nucleotide sequence of the Clostridium stercorarium xynA gene encoding xylanase A: identification of catalytic and cellulose binding domains

The nucleotides of the xynA gene of Clostridium stercorarium were sequenced. The structural gene consists of an open reading frame of 1533 bp encoding 511 amino acids with an M(r) of 56,519. The signal peptide cleavage site was identified by comparison with the N-terminal amino acid sequence of the enzyme produced by a recombinant Escherichia coli. Xylanase A consists of a catalytic domain belonging to family G at the N-terminus and two direct repeats of about 90 amino acids with a short spacing at the C-terminus. Deletion analysis showed that the repeated sequences were responsible for binding the enzyme to Avicel and were not essential for catalytic activity. The catalytic domain of this enzyme is highly homologous to xylanase A of Clostridium acetobutylicum (identity: 69%) and xylanase B of Bacillus pumilus (identity: 64%).

Purification and characterization of a thermostable beta-xylosidase from Thermoanaerobacter ethanolicus

A highly thermostable beta-xylosidase, exhibiting similarly high activities for arylxylose and arylarabinose, was purified (72-fold) to gel electrophoretic homogeneity from the ethanologenic thermophilic anaerobe Thermoanaerobacter ethanolicus. The isoelectric point is pH 4.6; the apparent molecular weight is around 165,000 for the native enzyme (gel filtration and gradient polyacrylamide gel electrophoresis) and 85,000 for the two subunits (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). The enzyme exhibited the highest affinity towards p-NO2-phenyl xyloside (pNPX) (substrate concentration for half-maximal activity = 0.018 mM at 82 degrees C and pH 5.0) but the highest specific activity with p-NO2-phenylarabinofuranoside. T(opt), 5 min, the temperature for the maximum initial activity in a 5-min assay of the purified enzyme, was observed around pH 5.9 and 93 degrees C; however at 65 and 82 degrees C, the pH optimum was 5.0 to 5.2, and at this pH the maximal initial activity was observed at 82 degrees C (pH 5.0 to 5.5). The pH curves and temperature curves for arylxylosides as substrates differed significantly from those for arylarabinosides as substrates. An incubation for 3 h at 82 degrees C in the absence of substrate reduced the activity to around 75%. At 86 degrees C the half-life was around 15 min. With pNPX as the substrate, an Arrhenius energy of 69 kJ/mol was determined. The N-terminal sequence did not reveal a high similarity to those from other published enzyme sequences.

Purification and properties of mycodextranase from Streptomyces sp. J-13-3

An enzyme hydrolyzing nigeran (alternating alpha-1,3- and alpha-1,4-linked glucan) was purified from the culture filtrate of Streptomyces sp. J-13-3, which lysed the cell wall of Aspergillus niger, by percipitation with ammonium sulfate and column chromatographies on DEAE-Sephadex A-50, CM-Sephadex C-50, chromatofocusing, and Sephadex G-100. The final preparation was homogenous in polyacrylamide gel electrophoresis (PAGE). The molecular weight of the enzyme was 68,000 by SDS-PAGE and gel filtration. The optimum pH and temperature for the enzyme activity were 6.0 and 50 degrees C, respectively. The enzyme was stable in the pH range from 6.0 to 8.0 and up to 50 degrees C. The enzyme activity was inhibited significantly by Hg+, Hg2+, and p-chloromercuribenzoic acid. The Km (mg/ml) for nigeran was 3.33. The enzyme specifically hydrolyzed nigeran into nigerose and nigeran tetrasaccharide by an endo-type of action, indicating it to be a mycodextranase (EC 3.2.1.61) that splits only the alpha-1,4-glucosidic linkages in nigeran.

Production of cellulolytic and xylanolytic enzymes during growth of the anaerobic fungus Piromyces sp. on different substrates

Piromyces sp. strain E2, an anaerobic fungus isolated from an Indian elephant (hindgut fermenter) was tested for its ability to ferment a range of substrates. The fungus was able to use bagasse, cellobiose, cellulose, fructose, glucose, lactose, mannose, starch, wheat bran, wheat straw, xylan and xylose. Formate and acetate were the main fermentation products after growth on these substrates. The amount of carbon found in the fermentation products of cultures, in which substrate digestion was complete averaged 88.5 mM, or 59% of the carbon offered as substrate. No growth was observed on other substrates tested. Lactose, starch, cellobiose and filter paper cellulose were good inducers of cellulolytic and xylanolytic enzymes. Cellulolytic and xylanolytic enzymes were produced constitutively by Piromyces strain E2, although enzyme activities were generally lower after growth on glucose and other soluble sugars. Complex substrates (bagasse, wheat bran, and wheat straw) were good inducers for xylanolytic enzymes but not for cellulolytic enzymes. The extracellular protein banding pattern after SDS-PAGE was therefore only slightly affected by the growth substrate. Identical beta-glucosidase and endoglucanase activity patterns were found after growth on different substrates. This indicated that differences in enzyme activities were not the result of secretion of different sets of isoenzymes although it remains possible that the relative amount of each isoenzyme produced is influenced by the growth substrate.

Production of carbohydrases by Sclerotium rolfsii

Coproduction of alpha-amylase, beta-amylase, amyloglucosidase, cellulase, xylanase, pectinase and beta-galactosidase by Sclerotium rolfsii was studied on various polysaccharides. Starch induced alpha-amylase, beta-amylase, amyloglucosidase and beta galactosidase; cellulose induced cellulase, xylanase, pectinase and beta-galactosidase; and pectin induced pectinase and beta-galactosidase. None of the enzymes studied except beta-galactosidase were induced on xylan. Group controlled mechanism for production of carbohydrases by Sclerotium rolfsii is suggested.

[Isolation and identification of a strain of Pseudomonas SP. producing insoluble glucan hydrolase]

A strain, CIB871, isolated from the natural world can hydrolyze insoluble glucan(IG) produced by S. mutans. This organism has been identified to be a strain of Pseudomonas SP. It grows well at 30 degrees C. The optimum medium for producing insoluble glucan hydrolase (IGase) is composed of 0.3% peptone, 0.03% IG and M1 salt solution (NH4)2 SO4 1mg/ml, MgSO4 50 micrograms/ml, FeCl2 50 micrograms/ml, K2HPO4 0.5mg/ml). The IGase production reached maximum when cultured for 65-70 hours.

Multiple copies of SUC4 regulatory regions may cause partial de-repression of invertase synthesis in Saccharomyces cerevisiae

Transformation to generate multiple copies of regulatory DNA sequences has been used to study the interactions between regulatory proteins and their target sequences, since a high copy number of these sequences may titrate trans-acting regulatory proteins. We have analyzed the synthesis of invertase in yeast strains carrying different SUC genes transformed with the multiple-copy plasmid pSH143, a derivative of pJDB207 containing the promoter and upstream regulatory sequences of SUC4. The results obtained seem to be strain dependent. Under repressing conditions a high copy number of SUC4 promoter regions may cause increased expression of the invertase genes resulting in the synthesis of external glycosylated protein. A similar result was obtained under de-repressing conditions since transformants from some strains showed higher levels of activity. These results suggest that transcriptional regulatory (negative) factors may become limiting when the copy number of their target DNA sequences is increased. This effect may depend on the amount of active repressor molecules as well as on their affinity for SUC4 upstream sequences. This is discussed on the basis of the nucleotide sequences of SUC promoters.