Construction of a genetically modified wine yeast strain expressing the Aspergillus aculeatus rhaA gene, encoding an alpha-L-rhamnosidase of enological interest.
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ABSTRACT:
SUBMITTER: Manzanares P
PROVIDER: S-EPMC309916 | biostudies-other | 2003 Dec
REPOSITORIES: biostudies-other
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Project description:The yeast Saccharomyces cerevisiae is the main species responsible for the process that involves the transformation of grape must into wine, with the initial nitrogen in the grape must being vital for it. One of the main problems in the wine industry is the deficiency of nitrogen sources in the grape must, leading to stuck or sluggish fermentations, and generating economic losses. In this scenario, an alternative is the isolation or generation of yeast strains with low nitrogen requirements for fermentation. In the present study, we carry out a genetic improvement program using as a base population a group of 70 strains isolated from winemaking environments mainly in Chile and Argentina (F0), making from it a first and second filial generation (F1 and F2, respectively) based in different families and hybrids. It was found that the trait under study has a high heritability, obtaining in the F2 population strains that consume a minor proportion of the nitrogen sources present in the must. Among these improved strains, strain "686" specially showed a marked drop in the nitrogen consumption, without losing fermentative performance, in synthetic grape must at laboratory level. When using this improved strain to produce wine from a natural grape must (supplemented and non-supplemented with ammonium) at pilot scale under wine cellar conditions, a similar fermentative capacity was obtained between this strain and a widely used commercial strain (EC1118). However, when fermented in a non-supplemented must, improved strain "686" showed the presence of a marked floral aroma absent for EC1118 strain, this difference being probably a direct consequence of its different pattern in amino acid consumption. The combination of the capacity of improved strain "686" to ferment without nitrogen addition and produce floral aromas may be of commercial interest for the wine industry.
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Project description:The food enzyme alpha-amylase (4-α-d-glucan glucanohydrolase; EC 3.2.1.1) is produced with a non-genetically modified Aspergillus niger (strain DP-Azb60) by Danisco US Inc. The food enzyme is free from viable cells of the production organism. The α-amylase is intended to be used in baking processes. Based on the maximum use levels, dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.503 mg TOS/kg body weight (bw) per day. Genotoxicity tests with the food enzyme did not indicate a genotoxic concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no-observed-adverse-effect level (NOAEL) at the highest dose of 1,000 mg TOS/kg bw per day that, compared with the estimated dietary exposure, results in a sufficiently high margin of exposure (of at least 1,988). Similarity of the amino acid sequence to those of known allergens was searched and one match was found to Asp o 21, an alpha-amylase from Aspergillus oryzae. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions upon dietary exposure to this food enzyme cannot be excluded, but the likelihood is considered low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.
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Project description:Abstract The food enzyme peroxidase (phenolic donor: hydrogen‐peroxide oxidoreductase, EC 1.11.1.7) is produced with the genetically modified Aspergillus niger strain MOX by DSM Food Specialties B.V. The genetic modifications do not give rise to safety concerns. The food enzyme is considered free from viable cells of the production organism and its DNA. The food enzyme is intended to be used in whey processing. Dietary exposure to the food enzyme total organic solids (TOS) was estimated to be up to 0.635 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not indicate a safety concern. The systemic toxicity was assessed by means of a repeated dose 90‐day oral toxicity study in rats. The Panel identified a no observed adverse effect level of 2,162 mg TOS/kg bw per day, the highest dose tested, which when compared with the estimated dietary exposure resulted in a margin of exposure of at least 3,405. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no match was found. The Panel considered that, under the intended conditions of use, the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns, under the intended conditions of use.
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Project description:The food enzyme glucoamylase (glucan 1,4-α-glucosidase; EC 3.2.1.3) is produced with the genetically modified strain of Aspergillus niger by Novozymes A/S. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and recombinant DNA. This glucoamylase is intended to be used in brewing processes and in starch processing for glucose syrups production. Residual amounts of total organic solids (TOS) are removed by the purification steps applied during the production of glucose syrups, consequently dietary exposure was not calculated. For brewing processes, based on the proposed maximum use levels, dietary exposure to the food enzyme-TOS was estimated to be below 3.627 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rodents. The Panel identified a no-observed-adverse-effect level (NOAEL) at the highest dose of 1,360 mg TOS/kg bw per day. Similarity of the amino acid sequence to those of known allergens was searched and one match was found. The Panel considered that, under the intended condition of use, the risk of allergic sensitisation and elicitation reactions upon dietary exposure to this food enzyme cannot be excluded, but the likelihood of such reactions to occur is considered to be low. Based on the data provided, the removal of TOS during the production of glucose syrups and the derived margin of exposure for brewing processes, the Panel concluded that this food enzyme does not raise safety concerns under the intended conditions of use.
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Project description:The food enzyme xylanase (4-β-d-xylan xylanohydrolase; EC 3.2.1.8) is produced with the genetically modified Aspergillus luchuensis Inui strain RF7398 by AB Enzymes GmbH. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and recombinant DNA. The food enzyme is intended to be used in baking and cereal-based processes. Based on the maximum use levels, dietary exposure to the food enzyme-Total Organic Solids (TOS) was estimated to be up to 0.008 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level of 1,000 mg TOS/kg bw per day, the highest dose tested, which when compared with the estimated dietary exposure, resulted in a high margin of exposure of at least 125,000. Similarity of the amino acid sequence of the food enzyme to those of known allergens was searched and one match was found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood of this occurring is considered to be low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.
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Project description:The food enzyme chymosin (EC 3.4.23.4) is produced with the genetically modified Aspergillus niger strain by Chr. Hansen. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its DNA. It is intended to be used in milk processing for cheese production and for the production of fermented milk products. Dietary exposure was estimated to be up to 0.09 mg total organic solids (TOS)/kg body weight (bw) per day in European populations. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level at the highest dose of 1,000 mg TOS/kg bw per day the highest dose tested, which when compared with the estimated dietary exposure, results in a margin of exposure of at least 10,600. Similarity of the amino acid sequence of the food enzyme to those of known allergens was searched and two matches with respiratory allergens were found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is considered low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.
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Project description:The food enzyme pectinesterase (pectin pectylhydrolase; EC 3.1.1.11) is produced with the genetically modified Aspergillus niger strain PME by DSM Food Specialties B.V. The genetic modifications do not give rise to safety concerns. The food enzyme is free from viable cells of the production organism and its recombinant DNA. It is intended to be used in fruit and vegetable processing, for juice production and fruit and vegetable processing for products other than juices. Dietary exposure to the food enzyme-total organic solids (TOS) was estimated to be up to 0.095 mg TOS/kg body weight (bw) per day in European populations. The toxicity studies were carried out with a xylanase obtained from A. niger strain XEA. The Panel considered this food enzyme as a suitable substitute for the pectinesterase to be used in the toxicological studies, because both production strains are derived from the same recipient strain, the location of the inserts is comparable, no partial inserts were present and the production methods are essentially the same. Genotoxicity tests did not indicate a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level (NOAEL) of 1,852 mg TOS/kg bw per day, the highest dose tested, resulting in a margin of exposure of at least 19,495. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and two matches with pollen allergens were found. The Panel considered that, under the intended conditions of use, the risk of allergic reactions upon dietary exposure to this food enzyme, particularly in individuals sensitised to pollen allergens, cannot be excluded. The Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.
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