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FAQ—Solarbio Microbial Media

FAQ Documentation—Microbial Media


Q01:Does microbial media come with an instruction manual?
A01:Typically, microbial media do not come with a separate instruction manual. The components and usage instructions are instead listed on the label of the bottle.

Q02:What is the product code for microbial media?
A02:Most product codes for microbial media begin with "LA".

Q03:Can microbial media be customized?
A03:Due to the complex manufacturing process involved in producing microbial media, customization to meet specific customer requirements is currently not feasible.

Q04:Preliminary pH adjustment of media
A04:Since the pH of media can change during the heating and sterilization process, a preliminary pH adjustment should be performed after all components have fully dissolved. For instance, beef extract may lower the pH by approximately 0.2, while intestinal extract may significantly increase it. Therefore, operators should pay close attention to developing experience in this step to ensure accurate final pH levels and maintain media quality. Following pH adjustment, the media should be boiled for several minutes to facilitate the precipitation of any sediment.

Q05:Reasons for media failing to solidify
A05:Potential causes include excessive heating during preparation, low pH leading to acid hydrolysis of the media, inaccurate weighing, incomplete dissolution of agar, and insufficient mixing of media components.

Q06:Reasons for incorrect pH values
A06:Overheating during preparation, poor water quality, contamination by external chemicals, incorrect temperature during pH measurement, improper calibration of the pH meter, and low-quality dehydrated media can all contribute to incorrect pH values.

Q07:Causes of precipitation in dissolved media
A07:Overheating during preparation, low quality of ingredients, poor quality of dehydrated media, and incorrect pH control can lead to precipitation in dissolved media.

Q08:Reasons for abnormal media color
A08:Abnormal media color can be attributed to overheating during preparation, poor water quality, low-quality dehydrated media, incorrect pH, and external contamination.

Q09:Causes of poor reproducibility in media inhibition
A09:Overheating during preparation, poor water quality, low-quality dehydrated media, incorrect use of ingredients (e.g., inaccurate weighing, incorrect additive concentrations) can all contribute to poor reproducibility in media inhibition.

Q10:What are the reasons for poor selectivity?
A10:Potential causes include excessive heating during preparation, low-quality dehydrated media, incorrect formulation usage, and incorrect addition of ingredients, such as adding them to overly heated media or using incorrect concentrations.

Q11:Is it better to boil and dissolve the media before autoclaving or to autoclave directly? There is confusion about this.
A11:Taking MacConkey Agar as an example, autoclaving after dissolution ensures no insoluble crystal violet or purple spots on the plates. In contrast, autoclaving without prior dissolution results in crystal violet and purple spots on the plates. Therefore, the correct approach is to boil and dissolve the media before autoclaving.

Q12:Why is the pH of the media not within the standard range?
A12:There are several potential reasons for this, which can be broadly categorized into 6 major points:
A. Poor quality (incorrect pH at the time of manufacture)
B. Sterilization issues (excessive temperature or duration during autoclaving, leading to caramelization of glucose and subsequent pH drop)
C. Shelf life (beyond expiration or clumping)
D. Water quality (use deionized, purified, or distilled water; avoid mineral or tap water)
E. Storage temperature (too high)
F. Direct sunlight exposure. Any of these six factors can cause deviations in media pH. In case of such issues, it is recommended to troubleshoot each factor until the problem is resolved.

Q13:Why does media char (carbonize) during autoclaving?
A13:Many laboratory personnel observe charring in media after sterilization. The primary reasons for this phenomenon include:
Sterilization temperature exceeding 121°C
Excessive sterilization duration
Overfilling the containers (should not exceed 80% of container capacity)
Prolonged storage of sterilized media in high-temperature environments.

Q14:How is the pH of media measured?
A14:It depends on the media's sterilization requirements:
For non-autoclavable media, measure the pH after boiling and cooling to 25°C (measure at least two points for solid media and take the average).
For autoclavable media, measure the pH after autoclaving and cooling to 25°C (measure at least two points for solid media and take the average).

Q15:Why does agar-containing media sometimes fail to solidify or solidify poorly when poured into plates?
A15:For autoclavable media, ensure even shaking before pouring to distribute the agar evenly (large agar molecules tend to settle at the bottom during cooling). For non-autoclavable media, boiling and dissolving the agar once may not be sufficient; repeating the process 3-5 times ensures complete dissolution.

Q16:Why is there a difference in powder color between different batches of the same product?
A16:The possible reasons for this phenomenon are analyzed as follows: The medium composition contains dyes or indicators, and the water content of the powdered medium can vary between batches. Generally, the water content is required to be ≤6%, and a higher water content results in a darker color. Additionally, longer processing times also contribute to the deepening of the color.

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