Patent Description:
Cyclodextrins are cyclic glucose oligosaccharides which are generally composed of α-(<NUM>,<NUM>) linked glucopyranose subunits. Common cyclodextrins include α-cyclodextrin (<NUM>-membered sugar ring), β-cyclodextrin (<NUM>-membered sugar ring) and γ-cyclodextrin (<NUM>-membered sugar ring). Cyclodextrins have many uses in industry, including in separation and extraction processes, as drug-delivery agents and as stabilisers in the food industry. Cyclodextrins have also been used as intermediates in the production of ethanol (e.g. <CIT>).

Cyclodextrins are generally produced by the enzymatic conversion of starch using enzymes such as cyclodextrin glucanotransferases. Cyclodextrin glucanotransferases (CGTases) are also known as cyclodextrin glycosyl transferases and cyclodextrin glucosyltransferases. These enzymes are generally only found in bacteria, particularly bacteria of the genus Bacillus (e.g. B. circulans, B. macerans and B. stearothermophilus).

It should be noted that wherein Clostridium thermohydrosulfuricus was previously classified as a Clostridial species, it has now been reclassified as Thermoanaerobacter thermohydrosulfuricus (<NPL>). The genus Thermoanaerobacter has now clearly established by sequence analysis and shown that it forms a separate and distinct genus from Clostridium sensu stricto (Cluster I) (<NPL>). <CIT> relates to a process for producing butanol by fermentation.

<CIT> relates to a process for producing butanol by fermentation.

Whilst CGTases are generally capable of catalysing more than one reaction, the most important activity is the production of cyclic dextrins from substrates such as starch, amylose and other polysaccharides. In this process, the polysaccharide chain is cleaved and the ends are joined by the CGTase in order to produce a cyclic dextrin, i.e. a cyclodextrin. The size of the cyclodextrin (i.e. the number of sugar residues it incorporates) is dependent on the distance apart of the ends.

There remains a need, however, for novel CGTases, particularly those that are capable of producing novel cyclodextrins.

In one embodiment, therefore, the invention provides a polypeptide, wherein the amino acid sequence of the polypeptide:.

The invention also provides a composition comprising the polypeptide of claim <NUM>.

The invention further provides a nucleic acid molecule comprising:.

preferably operably associated with one or more regulatory elements.

The invention also provides a vector comprising a nucleic acid molecule of claim <NUM>. Also provided is a host cell comprising a vector of claim <NUM>.

The invention further provides a method of hydrolysing a polysaccharide, comprising contacting the polysaccharide with a host cell as claimed in any one of claims <NUM>-<NUM>.

Also provided is a process for producing a cyclodextrin, the process comprising the steps:.

and optionally purifying and/or concentrating the obtained cyclodextrin.

The polypeptide of the invention may be isolated and/or purified. In particular, the polypeptide of the invention may be in a form which is isolated from one or more of the following: bacteria, polysaccharide (e.g. potato, starch), yeast extract, tryptone, other enzymes.

The polypeptide may be purified, i.e. the polypeptide may be substantially pure. In particular, the polypeptide may be at least <NUM>%, preferably at least <NUM>% and more preferably at least <NUM>% pure. Purity may be assessed using SDS-PAGE or any other appropriate method.

The invention also provides variants or derivatives of the polypeptide of SEQ ID NO: <NUM> or <NUM> as defined in claim <NUM>. The proteins of the invention may be altered in various ways including substitutions, deletions, truncations, and/or insertions of one or more (e.g. <NUM>-<NUM>, <NUM>-<NUM>) amino acids, preferably in a manner which does not substantially alter the biological activity of the polypeptide of the invention. Guidance as to appropriate amino acid changes that do not affect biological activity of the protein of interest may be found in the model of <NPL>. Conservative substitutions, such as exchanging one amino acid with another having similar properties, may be also made.

In particular, substitution of one hydrophobic amino acid such as isoleucine, valine, leucine or methionine for another may be made; or the substitution of one polar amino acid residue for another, such as arginine for lysine, glutamic for aspartic acid, or glutamine for asparagine, may be made.

One or more (e.g. <NUM>-<NUM>, <NUM>-<NUM>) amino acids in the polypeptides of the invention may be substituted by their corresponding D-amino acids, preferably at the N- and/or C-terminus.

In particular, the invention provides a variant of the polypeptide of SEQ ID NO: <NUM> or <NUM>, wherein the amino acid sequence of the variant comprises or consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% sequence identity with SEQ ID NO: <NUM> or <NUM>, preferably using the blastp method of alignment, and which codes for a cyclodextrin glucanotransferase.

The invention particularly relates to polypeptides of SEQ ID NO: <NUM> or <NUM> or to variants of the polypeptide of SEQ ID NO: <NUM> or <NUM> as defined herein, wherein the amino acid which corresponds to the amino acid at position <NUM> is a small amino acid, e.g. glycine, alanine, leucine, serine, threonine or valine, preferably glycine. The size of the amino acid residue at position <NUM> may be involved in determining the size of any cyclodextrin products or ratio of any cyclodextrin products.

The CGTases of the invention are capable of producing one or more cyclodextrins from polysaccharides, e.g. starch.

The CGTases fall within the general EC classification <NUM>. (hexosyltransferases). In some embodiments, the CGTase of the invention falls within classification EC <NUM>. <NUM> (cycloisomaltooligosaccharide glucanotransferase). In other embodiments of the invention, the CGTase falls within classification EC <NUM>. <NUM> (cyclomaltodextrin glucanotransferase).

The invention also provides a composition comprising or consisting essentially of a polypeptide of the invention. The polypeptide may be present in the composition in the absence of one or more of the following: bacteria, polysaccharide (e.g. potato, starch), yeast extract, tryptone.

The polypeptide of the invention may be provided in any suitable form, e.g. in lyophilised form or in a buffer.

As used herein, the term "nucleic acid molecule" refers to a DNA or RNA molecule, which might be single- or double-stranded. Preferably, the nucleic acid molecule is a DNA molecule, most preferably a double-stranded DNA molecule. The nucleic acid molecule is preferably one which contains no introns. The nucleic acid molecule may, for example, be intron-less genomic DNA or cDNA.

The nucleic acid molecule of the invention is preferably isolated or purified. As used herein, the term "isolated nucleic acid" means that the nucleic acid molecule is not contiguous with other genes with which it is normally associated in the natural source of the polypeptide-encoding nucleic acid. For example, an isolated nucleic acid of the invention will not be contiguous with a nucleic acid encoding a maltose binding protein periplasmic precursor; or it will not be contiguous with a nucleic acid encoding a neopullananse/cyclomaltodextrinase.

As used herein, the term "purified nucleic acid" means a nucleic acid molecule which is free or substantially free from other non-contiguous nucleic acids and/or is free or substantially free from one or more of the following: bacteria, polysaccharide (e.g. potato, starch), yeast extract, tryptone.

As used herein, the term "polysaccharide" or "polysaccharide substrate" refers preferably to a glucose-based polysaccharide, e.g. a starch or a starch-based material. Most preferably, the polysaccharide is starch or a starch-based material, e.g. corn, corn starch, corn mash, potato, potato starch, potato mash, potato peeling, potato chips, cassava, cassava starch, cassava chips, sago, sago starch or 'soluble starch'. e.g. as sold by Fisher / Sigma. In some embodiments of the invention, the nucleic acid molecule is a recombinant nucleic acid.

The nucleic acid of the invention is preferably operably associated with one or more regulatory elements, e.g. a promoter and/or a terminator element. As used herein the term "operably associated" or "operably linked" with a promoter means that the polypeptide-encoding region is transcribable from that promoter. The polypeptide-encoding region may, for example, be immediately <NUM>' to the promoter, in which case the promoter will direct the transcription of the coding sequence. Alternatively, the polypeptide-encoding region may be part of an operon in which case the associated or linked promoter will direct the transcription of all of the polypeptide-encoding regions within that operon.

The promoter or promoters are preferably ones which are operable in bacterial cells. More preferably, the promoters are bacterial promoters. Suitable promoters include inducible promoters, such as those that are inducible with specific sugars or sugar analogues, e.g. arabinose (e.g. lac, ara), those inducible with antibiotics (e.g. tetracycline, tet), those inducible with IPTG (e.g. trp, tac, Pspac), those inducible with heat (e.g. hsp70), those inducible with anaerobic induction (e.g. nisA, pfl, trc, IPL, IPR, T7), P11, ldh, sec (secDF), SV40 promoter, those inducible with xylose (e.g. Pxyl promoter), those inducible with osmotic shock, cell density (quorum sensing), anaerobicity, antibiotics, or growth phase. In some embodiments, the promoter is a constitutive promoter, e.g. the promoters for the thiolase gene (thl) or the permease operon (hfuC). The promoter may be one from Clostridia, e.g. a promoter from the pta/ptb genes. In yet other instances, the promoter may be one from a butanol and/or butyrate biosynthetic pathway gene.

The promoter may be an early onset promoter, i.e. a promoter from a gene which is upregulated during early exponential phase and reduced during transition phase and stationary phase. Examples of such promoters include promoters from glcK, hydA genes, or vitamin B12 synthesis, pta, ptb promoters.

The promoter may be a promoter from a gene which is normally active in the exponential phase of solventogenic bacteria. Examples include promoters from genes that are expressed constitutively throughout exponential phase, e.g. from glycolysis genes and those in the pathway to produce butyryl-CoA (pfk, gap, pgk, bcd).

Other examples of suitable promoters include the P2 (pta-ack, CAC1742, promoter), P6 (luxS, CAC2942, promoter) and P7 (CAC2941) promoters (<NPL>).

The P2 promoter is the promoter region from the operon encoding the phosphotransferase and the acetate kinase involved in acetate production from acetyl-CoA. The P6 promoter is the promoter region from a single chromosomal open reading frame encoding a LuxS homolog (CAC <NUM>), predicted to be involved in quorum sensing. The P7 promoter is the promoter region from a chromosomal operon (CAC <NUM> - <NUM>) encoded downstream and in the reverse orientation to CAC <NUM> and putatively involved in quorum sensing. The operon encodes a hydrolase (CAC <NUM>), a histidine kinase (CAC <NUM>), a response regulator (CAC <NUM>) and a hypothetical protein (CAC <NUM>).

In a further embodiment, the invention provides a variant of the nucleic acid molecule of SEQ ID NO: <NUM> or <NUM>, wherein the nucleotide sequence of the variant comprises or consists of an nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, <NUM>%, <NUM>%, <NUM>% or <NUM>% sequence identity with SEQ ID NO: <NUM> or <NUM>, preferably using the BLASTN method of alignment, and which encodes a cyclodextrin glucanotransferase.

Percentage amino acid sequence identities and nucleotide sequence identities may be obtained using the BLAST methods of alignment (<NPL>; and http://www. gov/BLAST). Preferably the standard or default alignment parameters are used.

Standard protein-protein BLAST (blastp) may be used for finding similar sequences in protein databases. Like other BLAST programs, blastp is designed to find local regions of similarity. When sequence similarity spans the whole sequence, blastp will also report a global alignment, which is the preferred result for protein identification purposes. Preferably the standard or default alignment parameters are used. In some instances, the "low complexity filter" may be taken off.

BLAST protein searches may also be performed with the BLASTX program, score=<NUM>, wordlength=<NUM>. To obtain gapped alignments for comparison purposes, Gapped BLAST (in BLAST <NUM>) can be utilized as described in<NPL>. Alternatively, PSI-BLAST (in BLAST <NUM>) can be used to perform an iterated search that detects distant relationships between molecules. (See Altschul et al. (<NUM>) supra). When utilizing BLAST, Gapped BLAST, PSI-BLAST, the default parameters of the respective programs may be used.

With regard to nucleotide sequence comparisons, MEGABLAST, discontiguous-megablast, and blastn may be used to accomplish this goal. Preferably the standard or default alignment parameters are used. MEGABLAST is specifically designed to efficiently find long alignments between very similar sequences. Discontiguous MEGABLAST may be used to find nucleotide sequences which are similar, but not identical, to the nucleic acids of the invention. The BLAST nucleotide algorithm finds similar sequences by breaking the query into short subsequences called words. The program identifies the exact matches to the query words first (word hits). The BLAST program then extends these word hits in multiple steps to generate the final gapped alignments. In some embodiments, the BLAST nucleotide searches can be performed with the BLASTN program, score=<NUM>, wordlength=<NUM>.

One of the important parameters governing the sensitivity of BLAST searches is the word size. The most important reason that blastn is more sensitive than MEGABLAST is that it uses a shorter default word size (<NUM>). Because of this, blastn is better than MEGABLAST at finding alignments to related nucleotide sequences from other organisms. The word size is adjustable in blastn and can be reduced from the default value to a minimum of <NUM> to increase search sensitivity.

A more sensitive search can be achieved by using the newly-introduced discontiguous megablast page (www. gov/Web/Newsltr/FallWinterO2/blastlab. This page uses an algorithm which is similar to that reported by <NPL>). Rather than requiring exact word matches as seeds for alignment extension, discontiguous megablast uses non-contiguous word within a longer window of template. In coding mode, the third base wobbling is taken into consideration by focusing on finding matches at the first and second codon positions while ignoring the mismatches in the third position. Searching in discontiguous MEGABLAST using the same word size is more sensitive and efficient than standard blastn using the same word size. Parameters unique for discontiguous megablast are: word size: <NUM> or <NUM>; template: <NUM>, <NUM>, or <NUM>; template type: coding (<NUM>), non-coding (<NUM>), or both (<NUM>).

In yet other embodiments, the nucleic acid of the invention is present in an operon with one or more genes which are involved in starch metabolism. Preferably, the nucleic acid of the invention is in an operon, wherein the nucleic acid of the invention is contiguous with one or more nucleic acid molecules which encode one or more of the following: a maltose binding protein periplasmic precursor, a neopullanase/cyclomaltodextrinase, one or more maltose/maltodextrin ABC transporter permease proteins, an alpha amylase catalytic domain protein and a glycogen debranching protein.

As used herein, the term "operon" refers to a segment of a nucleic acid molecule which comprises a linear sequence of two, three, four or more polypeptide-encoding regions which are all in the same <NUM>'-<NUM>' orientation and which are transcribable as a single (polycistronic) unit from an associated promoter. The promoter will in general be at the <NUM>' end of the operon.

In this case, transcription will be initiated from the first promoter and a single polycistronic mRNA transcript will be produced from the said two, three, four or more of the polypeptide-encoding regions.

The remaining polypeptide-encoding regions of the nucleic acid molecule may independently be operably linked together with a second promoter in a second operon, wherein the second operon is transcribable from the second promoter; or they may each be operably linked to and transcribable from further promoters.

Preferably, the operon has the sequence as given in SEQ ID NO: <NUM>, or a variant thereof having at least <NUM>%, preferably at least <NUM>%, <NUM>%, <NUM>% or <NUM>% sequence identity with SEQ ID NO: <NUM> using the BLASTN method of alignment.

The poeron may encode the following polypeptides in the order <NUM>'-<NUM>' (and each coding sequence being in the <NUM>'-<NUM>' direction): a maltose binding protein periplasmic precursor, an isocyclomaltooligosaccharide glucanotransferase (of the invention), a neopullanase/cyclomaltodextrinase, two maltose/maltodextrin ABC transporter permease proteins, an alpha amylase catalytic domain protein and a glycogen debranching protein.

The nucleic acid molecule of the invention or operon will preferably be in the form of a vector, particularly an expression vector, or a plasmid. The vector or plasmid may comprise one or more selectable markers and/or other genetic elements. Preferably, the vector or plasmid is less than 100Kb, more preferably less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or 20Kb. Preferably, the vector or plasmid additionally comprises one or more antibiotic resistance genes. Examples of such genes include genes conferring resistance to ampicillin, erythromycin, neomycin/kanamycin, tetracycline, chloramphenicol, spectinomycin, bleomycin and puromycin. The vector or plasmid may also comprise one or more genes conferring tolerance to one or more heavy metals, e.g. mercury. Other selectable markers include auxotrophy genes, e.g. genes for essential amino acids.

The vector or plasmid may also comprise an origin of replication, for example a Gram positive and/or a Gram negative origin of replication. The vector or plasmid may also comprise one or more insertion sequences, e.g. Tn10, Tn5, Tn1545, Tn916 and/or ISCb.

The nucleic acid molecule of the invention or operon or the plasmid or vector, may be introduced into a host cell, e.g. a micro-organism, preferably a bacterial cell.

The bacterial cell may, for example, be a Gram-positive or Gram-negative bacterium. The micro-organism may be a spore-forming bacterium or a saccharolytic bacterium.

The bacterium may be an aerobic or an anaerobic bacteria. Preferably it is an anaerobic bacteria. The bacteria may be a thermophilic bacterium. In yet other embodiments, the bacterium is a biphasic bacterium. As used herein, the term "biphasic" refers to a bacterium which has an acidogenic growth phase and a solventogenic growth phase. The term "acidogenic growth phase" refers to the ability of the bacterium to convert a substrate into R-COOH, for example, into acetate and/or butyrate. In this context, wherein R is an aliphatic C1-C5, preferably C1-<NUM>, alkyl or alkenyl group. The term "solventogenic growth phase" refers to the ability of the bacterium to convert the RCOOH into a solvent, preferably into one or more of acetone, ethanol and/or butanol.

The bacterium may be a solvent-producing bacterium. As used herein, the term "solvent-producing" means that the bacterium is one which is capable of producing a solvent, preferably a solvent such as acetone, ethanol, propanol and/or butanol. The bacterium may be capable of producing ethanol, acetone and butanol. Preferably, the bacteria is a butanol-producing bacteria or a butanol-tolerant bacterium.

In some preferred embodiments, the bacterium is of the genus Clostridium. Preferred Clostridium species include C. acetobutylicum, C. aurantibutyricum, C. beijerinckii, C. thermocellum, C. thermobutyricum, C. pasteurianum, C. kluyveri, C. saccharobutylicum, C. thermosaccharolyticum, C. saccharolyticum, C. tyrobutyricum, C. butyricum, C. puniceum, C. diolis and C.

In some embodiments, the bacteria is a Cluster I Clostridia. Preferred examples of Cluster I Clostridia include C. acetobutylicum, C. arbusti, C. argentinense, C. beijerinckii, C. butyricum, C. cellulovorans, C. kluyveri, C. pasteurianum, C. puniceum, C. saccharobutylicum, C. saccharoperbutylacetonicum and C. tyrobutyricum.

In some embodiments of the invention, a recombinant bacterial host cell comprises a nucleic acid molecule integrated into the host cell genome, wherein the nucleotide sequence of the nucleic acid molecule: (a) encodes the amino acid sequence set forth in SEQ ID NO: <NUM> or <NUM>; (b) encodes a CGTase having at least <NUM>% amino acid sequence identity with SEQ ID NO: <NUM> or <NUM>; (c) is set forth in SEQ ID NO: <NUM> or <NUM>; or (d) has at least <NUM>% sequence identity with the nucleotide sequence set forth in SEQ ID NO: <NUM> or <NUM>, and which encodes a CGTase, wherein the recombinant host cell is not Clostridium saccharoperbutylacetonicum N1-<NUM> (HMT) or Clostridium saccharoperbutylacetonicum N1-<NUM>.

In some embodiments of the invention, a recombinant bacterial host cell comprises a nucleic acid molecule integrated into the host cell genome, wherein the nucleotide sequence of the nucleic acid molecule: (a) encodes the amino acid sequence set forth in SEQ ID NO: <NUM> or <NUM>; (b) encodes a CGTase having at least <NUM>% amino acid sequence identity with SEQ ID NO: <NUM> or <NUM>; (c) is set forth in SEQ ID NO: <NUM> or <NUM>; or (d) has at least <NUM>% sequence identity with the nucleotide sequence set forth in SEQ ID NO: <NUM> or <NUM>, and which encodes a CGTase, wherein the nucleic acid molecule is operably associated with a constitutive promoter.

In some instances, the host cell is not C. saccharoperbutylacetonicum N1-<NUM>. In other instances, the host cell is not C. saccharoperbutylacetonicum N1-<NUM>(HMT). In yet other instances, the host cell is not C. saccharoperbutylacetonicum N1-<NUM>.

The bacterium may be of the genus Bacillus or Geobacillus.

The invention further provides a process for making a recombinant bacterial host cell, comprising introducing a nucleic acid molecule of the invention, or an operon or a vector of the invention, into a bacterial host. Methods of introducing nucleic acid molecules, operons, plasmids and vectors into bacterial hosts are well known in the art. These include transformation, transfection and electroporation techniques.

The invention also provides a recombinant bacterial host cell comprising a vector as defined in claim <NUM>.

The nucleic acid molecule or operon may be present in the cytoplasm of the host, e.g. as a plasmid or a vector, or it may be integrated in the host genome.

With regard to the bacterial host cell comprising a vector as defined in claim <NUM>, the vector may be present in the cytoplasm of the cell.

With regard to the bacterial host cell comprising a vector as defined in claim <NUM>, the vector may be stably integrated into the genome of the cell.

The invention also provides a method of hydrolysing a polysaccharide, comprising contacting the polysaccharide with a host cell of the invention, preferably a recombinant bacterial host cell of the invention.

A method of hydrolysing a polysaccharide may comprise contacting the polysaccharide with a host cell of the invention which has been stably transformed with a nucleic acid or operon or vector or plasmid of the invention, such that the host cell expresses a CGTase and optionally one or more other polypeptides which are involved in starch metabolism.

As used herein, the term "polypeptides which are involved in starch metabolism" includes maltose binding protein periplasmic precursors, isocyclomaltooligosaccharide glucanotransferases, neopullanase/cyclomaltodextrinases, maltose/maltodextrin ABC transporter permease proteins, alpha amylase catalytic domain proteins and glycogen debranching proteins.

Preferably, the host cell is also capable of converting the hydrolysed polysaccharide to an acid such as R-COOH, for example into acetate and/or butyrate. Optionally, the host cell is also capable of converting the RCOOH into a solvent, preferably into one or more of acetone, ethanol and/or butanol.

The invention also provides a method of producing a solvent comprising the steps:.

wherein the host cell is also capable of converting hydrolysed polysaccharide to acetate and/or butyrate. Optionally, the host cell is also capable of converting the acetate and/or butyrate into one or more of acetone, ethanol and/or butanol.

Preferably, step (i) is carried out under conditions wherein the host cell expresses the CGTase and wherein the CGTase hydrolyses some or all of the polysaccharide substrate.

The host cell may be one which is naturally capable of converting the hydrolysed polysaccharide to an acid such as R-COOH and/or which is naturally capable of converting the RCOOH into a solvent. Alternatively, the host cell is one which has been transformed with one or more nucleic acid molecules encoding polypeptides which are capable of converting the hydrolysed polysaccharide to an acid such as R-COOH and/or which are capable of converting the RCOOH into a solvent.

The invention also provides a process for producing a cyclodextrin, the process comprising the steps:.

Preferably, the polysaccharide substrate a glucose-based polysaccharide. More preferably, the polysaccharide substrate is starch or a starch-based material, e.g. corn mash, potato mash, potato peeling.

The present invention is further illustrated by the following Examples, in which parts and percentages are by weight and degrees are Celsius, unless otherwise stated. It should be understood that these Examples, while indicating preferred embodiments of the invention, are given by way of illustration only.

saccharoperbutylacetonicum was grown on various substrates. Supernatant samples were taken after <NUM> hours, concentrated and then spotted onto a starch plate. Supernatant from C. saccharoperbutylacetonicum grown on glucose does not show any hydrolytic activity, whereas supernatant from starch and corn does (<FIG>).

These supernatant samples were also analysed by SDS-PAGE and an induced enzyme was identified (<FIG>).

The induced peptide was excised from the SDS-PAGE gel and identified by mass spectrometry as being an isocyclomaltooligosaccharide glucanotransferase (CGTase).

The portion of the C. saccharoperbutylacetonicum genome coding for the CGTase was sequenced. It was found that the CGTase is located within a starch metabolism operon (<FIG> and SEQ ID NO: <NUM>).

The amino acid sequence of the CGTase from C. saccharoperbutylacetonicum N1-<NUM>(HMT) is given in SEQ ID NO: <NUM>. The corresponding nucleic acid sequence is given in SEQ ID NO: <NUM>.

The amino acid sequence of the CGTase from C. saccharoperbutylacetonicum N1-<NUM> is given in SEQ ID NO: <NUM>. The corresponding nucleic acid sequence is given in SEQ ID NO: <NUM>.

Based on sequence alignments and homology searches, the CGTase from C. saccharoperbutylacetonicum appears to be a novel enzyme. A number of features make it different from the well-characterised α-, β-, and γ-CGTases for example, protein alignments show it clusters with CGTases from B. circulans and Arthrobacter which have been characterised and do not form the standard α-, β- or γ-cyclodextrins containing <NUM>, <NUM> or <NUM> glucose units with α1-<NUM> linkages (<FIG>). Instead this class of CGTase enzymes appears to be much less conserved and converts starch to cyclodextrins containing <NUM>, <NUM> or <NUM> glucose units with both α1-<NUM> and α1-<NUM> linkages. A key feature of these enzymes is a highly conserved residue required for efficient cyclisation. The α-, β-, and γ-CGTases all have tyr or phe at this position. α- amylases have a small residue at this equivalent position, as do the CGTases from B. circulans, Arthrobacter and C. saccharoperbutylacetonicum (<FIG>).

Based on these sequence comparisons, it is inferred that the CGTase from C. saccharoperbutylacetonicum does not convert starch through the well characterised α-, β-, γ-cyclodextrin route. Instead it appears to cyclise starch using a different mechanism.

Proteins secreted into the supernatant during a C. saccharoperbutylacetonicum fermentation on a starch-based substrate were fractionated using ammonium sulphate cuts. The starch degradation activity was followed by spotting each fraction onto a starch plate and staining with iodine to detect zones of clearing. The fraction containing starch hydrolysis activity was added to a flask containing <NUM>/L starch solution and incubated overnight at <NUM> in a shaking incubator. The starch solution was known to contain some linear dextrins.

In the morning, a mixture of starch and various starch hydrolysis products were detected in the flask, including linear- and cyclo-dextrins.

The hydrolysis products from Example <NUM> were detected by HPLC. As shown in <FIG>, various starch hydrolysis products were detected, including linear- and cyclo-dextrins.

The <NUM>% ammonium sulphate 'cut' was also separated on an SDS-PAGE gel and the bands were isolated. Mass spectrometry was used to confirm the CGTase was still present in this fraction (data not shown).

The CGTase enzyme from C. saccharoperbutylacetonicum produced a cyclic dextrin with an elution profile which was different from known α-, β- and γ- cyclodextrins (<FIG>). The elution profile was also clearly different to the elution profile one would expect to see if the strain was converting starch to dextrins and glucose using α-amylase and glucoamylase.

Claim 1:
A polypeptide, wherein the amino acid sequence of the polypeptide:
(a) comprises the amino acid sequence set forth in SEQ ID NO: <NUM> or <NUM>;
(b) comprises an amino acid sequence which has at least <NUM>% sequence identity with SEQ ID NO: <NUM> or <NUM> and which codes for a cyclodextrin glucanotransferase;
(c) is encoded by the nucleotide sequence set forth in SEQ ID NO: <NUM> or <NUM>; or
(d) is encoded by a nucleotide sequence which has at least <NUM>% sequence identity with the nucleotide sequence set forth in SEQ ID NO: <NUM> or <NUM>, and which encodes a cyclodextrin glucanotransferase.