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Dextrose Starch Agar | Medium for Amylolytic Microorganisms | AS‑1204
$89.00 AUD
Dextrose Starch Agar (DSA)
GC Agar Base & General-Purpose Nutrient Medium | Neisseria, Starch Hydrolysis, Heterotrophic Cultivation | Cat. No. AS-1204
Cat. No. AS-1204 pH 7.2 ± 0.2 65 g/L Gelatin 20 g/L | Starch 10 g/L ✓ GC Agar Base — Neisseria ✓ Sigma D3060 Equivalent 🇦🇺 Made in Melbourne ⚡ Same-Week Dispatch
Cat. No.
AS-1204
pH (25°C)
7.2 ± 0.2
Dissolution
65 g/L
Starch
10.0 g/L
Sterilisation
121°C / 15 min
📄 Full DocumentationCOA, TDS & SDS every batch
🇦🇺 Australian StockNo import delays
⚡ Same-Week DispatchMelbourne warehouse
🔬 Technical SupportDirect from our team
Overview
Dextrose Starch Agar (DSA, AS-1204) is a versatile nutrient medium used primarily as a GC Agar Base for the cultivation of Neisseria gonorrhoeae and N. meningitidis when supplemented with haemoglobin and growth factors (IsoVitaleX or equivalent). It is also widely used for starch hydrolysis testing (amylase activity detection with iodine flooding), general heterotrophic bacterial cultivation, and colony morphology differentiation in environmental, food, and clinical microbiology laboratories.
The unique formula combines a rich proteose peptone nitrogen source with soluble starch as both a hydrolysis substrate and energy reserve, gelatin as an additional protein source, disodium phosphate as a pH buffer, and low dextrose (2 g/L) for carbohydrate supplementation without the intense fermentation seen in high-sugar media.
Mode of Action — Three Functions in One Medium
1. GC Agar Base (with supplements): DSA provides the basal nutrient platform for fastidious Neisseria spp. Proteose peptone supplies the complex nitrogen, amino acids, and growth cofactors required. With addition of 2% haemoglobin and IsoVitaleX (or Supplement B), the medium supports N. gonorrhoeae and N. meningitidis growth — organisms that require specific amino acids and coenzymes not present in simpler media.
2. Starch Hydrolysis Testing (differential use): Soluble starch (10 g/L) is the substrate for amylase-producing bacteria. After incubation, flood the plate with Gram's iodine solution. Starch-positive organisms (amylase producers) show a clear halo around the colony where starch has been hydrolysed. Starch-negative organisms remain surrounded by the blue-black iodine-starch complex. This is used for identification of Bacillus, Clostridium, Pseudomonas, and environmental isolates.
3. General Nutrient Base: Without supplementation, DSA supports broad heterotrophic bacterial growth from food, water, soil, and industrial samples. The gelatin (20 g/L) also allows gelatinase testing — pour melted agar into gelatin agar medium or observe liquefaction.
2. Starch Hydrolysis Testing (differential use): Soluble starch (10 g/L) is the substrate for amylase-producing bacteria. After incubation, flood the plate with Gram's iodine solution. Starch-positive organisms (amylase producers) show a clear halo around the colony where starch has been hydrolysed. Starch-negative organisms remain surrounded by the blue-black iodine-starch complex. This is used for identification of Bacillus, Clostridium, Pseudomonas, and environmental isolates.
3. General Nutrient Base: Without supplementation, DSA supports broad heterotrophic bacterial growth from food, water, soil, and industrial samples. The gelatin (20 g/L) also allows gelatinase testing — pour melted agar into gelatin agar medium or observe liquefaction.
Primary Applications
🧬
GC Agar Base
Neisseria gonorrhoeae & meningitidis with supplements
🧪
Starch Hydrolysis
Amylase detection — iodine flood after incubation
🌿
Environmental
Heterotrophic bacteria from water, soil, surfaces
🍕
Food Microbiology
General bacterial enumeration and isolation
📊
Teaching & Research
Starch hydrolysis demonstrations, colony morphology
🔬
Industrial QC
Amylase-producing organism screening
Starch Hydrolysis Test Protocol
1
Inoculate the DSA plate with the test organism(s) by point inoculation or streaking. Leave adequate space between colonies for halo visualisation.
2
Incubate at 35–37°C for 24–48 hours (or at the appropriate temperature for the organism being tested).
3
After incubation, flood the plate with Gram's iodine solution (Lugol's iodine). Pour enough to cover the agar surface. Wait 30–60 seconds.
4
Pour off excess iodine and observe immediately (result fades on standing).
Positive: Clear/white halo around colony = starch hydrolysed by amylase.
Negative: Blue-black colouration around and under colony = starch intact.
Positive: Clear/white halo around colony = starch hydrolysed by amylase.
Negative: Blue-black colouration around and under colony = starch intact.
ⓘ Starch hydrolysis positive organisms include: Bacillus subtilis, Bacillus amyloliquefaciens, Clostridium spp., Pseudomonas spp. (some), Aspergillus spp., many environmental Actinomycetes. Negative: E. coli, Staphylococcus aureus, Pseudomonas aeruginosa.
GC Agar Preparation (Neisseria)
Standard GC Agar for N. gonorrhoeae:
1. Prepare DSA base at 65 g/L. Autoclave 121°C / 15 min. Cool to 50–55°C.
2. Add aseptically: 2% haemoglobin solution (equal volume, pre-sterilised) to form chocolate agar colour.
3. Add aseptically: IsoVitaleX Enrichment (or Supplement B) at 1% v/v — supplies NAD, glutamine, coenzymes, thiamine pyrophosphate.
4. Mix gently and pour plates immediately. Incubate inoculated plates at 35–37°C in 5% CO₂ for 24–48h.
Result: N. gonorrhoeae grows as small, translucent, glistening colonies on the chocolate-coloured medium.
1. Prepare DSA base at 65 g/L. Autoclave 121°C / 15 min. Cool to 50–55°C.
2. Add aseptically: 2% haemoglobin solution (equal volume, pre-sterilised) to form chocolate agar colour.
3. Add aseptically: IsoVitaleX Enrichment (or Supplement B) at 1% v/v — supplies NAD, glutamine, coenzymes, thiamine pyrophosphate.
4. Mix gently and pour plates immediately. Incubate inoculated plates at 35–37°C in 5% CO₂ for 24–48h.
Result: N. gonorrhoeae grows as small, translucent, glistening colonies on the chocolate-coloured medium.
DSA vs Comparable General Nutrient Media
| Medium | Key Components | Starch | Gelatin | Best For |
|---|---|---|---|---|
| DSA (AS-1204) ★ | Proteose Peptone 15g + Starch 10g + Gelatin 20g | ✓ 10 g/L | ✓ 20 g/L | GC Agar Base; starch hydrolysis; heterotrophs |
| Nutrient Agar (AS-1309) | Peptone 5g + Beef Extract 3g | ✕ | ✕ | Non-fastidious general cultivation |
| Tryptic Soy Agar (AS-1371) | Casein 15g + Soy 5g + NaCl 5g | ✕ | ✕ | USP/EP sterility, general enrichment |
| Starch Agar (plain) | Peptone + Starch only | ✓ | ✕ | Starch hydrolysis only; no gelatin |
| Plate Count Agar (AS-1329) | Tryptone 5g + Yeast Extract 2.5g + Glucose 1g | ✕ | ✕ | Total viable count (TVC) — food/water |
FAQs
❓ What is the role of gelatin in this formula?
Gelatin (20 g/L) serves two functions. First, it is an additional protein/nitrogen source providing amino acids from partial hydrolysis during autoclaving. Second, it can be used for gelatinase activity testing — some protocols use DSA to observe gelatin liquefaction by gelatinase-producing organisms. At pH 7.2 and normal incubation temperatures, the agar remains solid; gelatin liquefaction produces a characteristic zone around active colonies.
❓ Why is the dextrose concentration so low (2 g/L)?
The low dextrose (2 g/L) provides a minimal carbohydrate energy source without promoting intense fermentation that would drop the pH and affect starch hydrolysis test results or suppress fastidious organisms. In GC Agar applications, high fermentable sugar can inhibit Neisseria spp. The primary carbohydrate energy reserve in this medium is the soluble starch (10 g/L), not dextrose.
❓ Is DSA the same as GC Agar Base?
Yes — Dextrose Starch Agar is widely used as a GC Agar Base (GC = gonococcal culture). The formula (Proteose Peptone + Soluble Starch + Gelatin + Dextrose + NaCl + Na₂HPO₄ + Agar) is the same formulation commercially sold as GC Medium Base by Sigma-Aldrich (D3060) and equivalent suppliers. With haemoglobin and IsoVitaleX supplementation it becomes the standard Chocolate GC Agar for Neisseria gonorrhoeae.
❓ What iodine solution should I use for the starch hydrolysis test?
Gram's iodine (Lugol's iodine): iodine 1g + potassium iodide 2g in 300 mL distilled water. This is the standard reagent for starch hydrolysis testing on solid media. Flood the plate, wait 30–60 seconds, pour off the excess, and read immediately — the clear halo fades quickly.
❓ Is AS-1204 equivalent to Sigma-Aldrich D3060?
Yes — AS-1204 follows the same formula: Proteose Peptone 15g, Dextrose 2g, Soluble Starch 10g, NaCl 5g, Na₂HPO₄ 3g, Gelatin 20g, Agar 10g = 65 g/L, pH 7.2 ± 0.2. Full COA included with every batch.
Cross-Reference / Equivalents
| Manufacturer | Product Name | Cat. No. |
|---|---|---|
| Sigma-Aldrich / Merck | Dextrose Starch Agar (GC Medium Base) | D3060 |
| Merck Millipore | GC Agar Base | 1.10210 |
| HiMedia | Dextrose Starch Agar | M263 |
| Thermo Scientific / Oxoid | GC Agar Base | CM0367 |
Related Products
Product Specifications
| Product Name | Dextrose Starch Agar (DSA) |
| Catalogue Number | AS-1204 |
| Synonyms | GC Agar Base; GC Medium Base; Chocolate Agar Base; Dextrose Starch Medium; Neisseria Culture Agar Base |
| Commercial Equivalents | Sigma-Aldrich D3060 | Merck 1.10210 | HiMedia M263 | Oxoid CM0367 |
| Medium Type | General-purpose nutrient agar; GC Agar Base (when supplemented) |
| Dissolution | 65 g/L in distilled or deionised water |
| Final pH at 25°C | 7.2 ± 0.2 |
| Sterilisation | Autoclave 121°C for 15 minutes |
| Appearance (powder) | Light beige to cream, free-flowing homogeneous powder |
| Appearance (prepared agar) | Pale amber, clear to slightly opalescent; firm gel |
| Storage (powder) | 15–30°C, dry, tightly sealed, away from direct sunlight |
| Storage (prepared plates) | 2–8°C, inverted, protected from light; use within 2 weeks |
| HS Tariff Code | 3821.00.00 |
Formula — Per Litre (Sigma-Aldrich D3060 / Merck Reference)
| Ingredient | g / L | Function |
|---|---|---|
| Proteose Peptone | 15.0 | Primary nitrogen source — long-chain peptides, amino acids, growth factors for fastidious organisms |
| Soluble Starch | 10.0 | Polysaccharide energy reserve; substrate for amylase (starch hydrolysis) testing |
| Gelatin | 20.0 | Additional protein/nitrogen source; substrate for gelatinase activity testing |
| Sodium Chloride (NaCl) | 5.0 | Osmotic balance — physiological ionic strength |
| Disodium Phosphate (Na₂HPO₄) | 3.0 | pH buffer — maintains pH 7.2 ± 0.2 during growth |
| Dextrose (D-Glucose) | 2.0 | Supplementary carbon/energy source; low level avoids excessive acid production |
| Agar | 10.0 | Solidifying agent (lower than standard 15 g/L — softer gel for colonial spread) |
| Total | 65.0 g/L | pH 7.2 ± 0.2 at 25°C — Autoclave 121°C / 15 min |
ⓘ Note on agar level (10 g/L): DSA uses a lower agar concentration (10 g/L) than standard media (15 g/L), producing a slightly softer gel. This is consistent with the Sigma D3060 reference formula and optimises surface characteristics for Neisseria colony morphology observation.
Preparation Protocol
1
Suspend 65 g of dehydrated DSA (AS-1204) in 1 litre of purified or distilled water.
2
Mix well. Heat with frequent agitation and bring to a gentle boil for 1 minute until fully dissolved.
3
Sterilise by autoclaving at 121°C for 15 minutes.
4
Cool to 50–55°C. For GC Agar: add supplements aseptically (haemoglobin 2% + IsoVitaleX 1%) and mix gently. For plain DSA: pour directly.
5
Pour approximately 20 mL per 90 mm Petri dish. Allow to solidify. Store prepared plates inverted at 2–8°C; use within 2 weeks.
Quality Control Organisms
| Organism (ATCC) | Application | Incubation | Expected Result |
|---|---|---|---|
| Neisseria gonorrhoeae (49226) | GC Agar Base (+ supplements) | 35°C / 5% CO₂ / 24–48h | Small, translucent, glistening colonies ✓ |
| Escherichia coli (25922) | General growth (plain DSA) | 35°C / 18–24h | Good growth; starch hydrolysis negative ✓ |
| Bacillus subtilis (6633) | Starch hydrolysis test | 35°C / 24–48h | Good growth; clear halo with iodine (positive) ✓ |
| Staphylococcus aureus (25923) | General growth (plain DSA) | 35°C / 18–24h | Good growth; starch hydrolysis negative ✓ |
Literature & References
| # | Reference |
|---|---|
| 1 | Sigma-Aldrich / Merck. Dextrose Starch Agar (GC Medium Base), Cat. D3060. Specification sheet; current edition. [Reference formula] |
| 2 | Murray PR, et al. Manual of Clinical Microbiology. 12th ed. ASM Press; 2019. [GC Agar for Neisseria culture] |
| 3 | CLSI. Performance Standards for Antimicrobial Susceptibility Testing of Neisseria gonorrhoeae. CLSI M100; current edition. |
| 4 | Atlas RM. Handbook of Microbiological Media. 4th ed. CRC Press; 2010. [Dextrose Starch Agar and starch hydrolysis methodology] |
| 5 | ISO 11133:2014. Culture media performance testing. Geneva: ISO; 2014. |
📄 Full 16-section GHS SDS available (Australian WHS Regulations 2023 / GHS 7th Edition) — support@ausamics.com.au
Section 1 — Identification
| Product Name | Dextrose Starch Agar (DSA) |
| Catalogue No. | AS-1204 |
| Supplier | AuSaMicS Pty Ltd | ABN 56 676 640 467 |
| Address | 31 Longview CT, Thomastown VIC 3074, Australia |
| Emergency | Poisons Information Centre: 13 11 26 (24 hr) |
| Phone | +61 412 520 598 | support@ausamics.com.au |
Section 2 — Hazard Identification (GHS 7th Ed / WHS 2023)
| GHS Classification | NOT classified as a hazardous substance under Australian WHS Regulations 2023 at intended use concentrations. |
| Signal Word | None required |
| Other Hazards | Combustible dry powder. Dust may cause mild respiratory irritation. No significant chemical hazard at normal laboratory handling levels. |
Composition Summary
| Component | g/L | CAS | Hazard |
|---|---|---|---|
| Proteose Peptone | 15.0 | 73049-73-7 | Not hazardous |
| Soluble Starch | 10.0 | 9005-84-9 | Not hazardous |
| Gelatin | 20.0 | 9000-70-8 | Not hazardous |
| Sodium Chloride | 5.0 | 7647-14-5 | Not hazardous |
| Disodium Phosphate | 3.0 | 7558-79-4 | Not hazardous |
| Dextrose | 2.0 | 50-99-7 | Not hazardous |
| Agar | 10.0 | 9002-18-0 | Not hazardous |
| Respiratory PPE | P1 filter when weighing bulk powder |
| Eye Protection | Safety glasses when handling dry powder |
| Skin / Gloves | Nitrile gloves when handling inoculated cultures |
| Waste (plain DSA) | Autoclave inoculated plates (121°C / 15 min) before disposal as general microbiological waste |
| Transport | Not dangerous goods — ADG, IMDG, IATA |
| Regulatory | Australian WHS Regulations 2023 | GHS 7th Edition | AICIS compliant |
⚠️ Biosafety — GC Agar use with Neisseria: When used as GC Agar Base for Neisseria gonorrhoeae or N. meningitidis, handle inoculated plates per BSL-2 requirements. N. meningitidis cultures require particular care — laboratory-acquired meningococcal disease has been reported from aerosol exposure. All manipulations must be performed in a biological safety cabinet. Consult your institutional biosafety officer and applicable WHS requirements.
Quality Specifications
| Parameter | Specification | Method |
|---|---|---|
| Appearance (powder) | Light beige to cream, free-flowing, homogeneous | Visual |
| Appearance (prepared agar) | Pale amber, clear to slightly opalescent; firm gel | Visual after dissolution |
| pH (prepared, 25°C) | 7.2 ± 0.2 | pH meter (calibrated) |
| Dissolution | Complete at 65 g/L with boiling | Visual |
| Moisture Content | ≤5.0% (w/w) | Loss on drying |
| Growth — E. coli ATCC 25922 | Good growth at 35°C / 18–24h; ≤100 CFU inoculum | ISO 11133:2014 |
| Growth — S. aureus ATCC 25923 | Good growth at 35°C / 18–24h; ≤100 CFU inoculum | ISO 11133:2014 |
| Starch hydrolysis function | Clear halo with iodine around B. subtilis ATCC 6633 colonies | Iodine flooding test |
| Batch COA | Available every production lot | Included with order |
Manufacturing & Documentation
Manufactured by AuSaMicS Pty Ltd
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Formulated per Sigma-Aldrich D3060 / Merck 1.10210 reference specification
✓ Batch-level QC per ISO 11133:2014 — pH, growth promotion, appearance
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch, no import delays
✓ Technical support from our microbiology team
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Formulated per Sigma-Aldrich D3060 / Merck 1.10210 reference specification
✓ Batch-level QC per ISO 11133:2014 — pH, growth promotion, appearance
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch, no import delays
✓ Technical support from our microbiology team
⚠️ For laboratory and research use only. Not for food, veterinary, therapeutic, or direct human use. Handle inoculated cultures per institutional biosafety requirements.