Amino acids are de-aminized (Removal of the amino (--NH2) group) by microorganisms, converting amino acids into carboxylic acids that are utilizable for ATP synthesis. Carboxylic acids, not like amino acids, can be channeled into substrate oxidizing pathways such as Glycolysis or Krebs cycle. The main aim of substrate oxidation is synthesis of ATP. However, many intermediate substrates such as glyceraldehyde-3-phosphate found in substrate oxidizing pathways are often used as precursors of anabolic activities, i.e. for the synthesis of organic compounds in cells. In that sense, amino acids are ultimately used as a carbon source as well.

Amino acids are used majorly as sources of nitrogen but some microorganisms can also use it as source of carbon.  You can use NH3 or Uria or NO3 depending on the assimilation ability of your microbe as sole source of nitrogen.  

Amino acids are de-aminized (Removal of the amino (--NH2) group) by microorganisms, converting amino acids into carboxylic acids that are utilizable for ATP synthesis. Carboxylic acids, not like amino acids, can be channeled into substrate oxidizing pathways such as Glycolysis or Krebs cycle. The main aim of substrate oxidation is synthesis of ATP. However, many intermediate substrates such as glyceraldehyde-3-phosphate found in substrate oxidizing pathways are often used as precursors of anabolic activities, i.e. for the synthesis of organic compounds in cells. In that sense, amino acids are ultimately used as a carbon source as well.

Many aminoasids may be used as neuroactive substances, as resoures for  energy metabolism and participate in the epigenomic regulation (directly and/or indirectly)

The amino acids can be used like N-sources by the amino group, and like C-sources when are de-aminized to organics acids.

Generally amino acids are nitrogen containing organic compounds and the specific side groups present in amino acids can influence the enzyme synthesis and growth of microorganisms considerably.  

For nitrogen sources you can use ammonium sulphate and chloride, all kinds of nitrate salts, and you can also use organic nitrogen sources like peptone, tryptone, beef extract etc. Many papers focused on sodium nitrate and ammonium sulphate giving good results for microbial growth and enzyme production also.

If it is to be assumed that the question concerning the nutritional value of amino acids is not a general one but a specific concern for the preparation of a culture medium to satisfy the needs of a particular microorganism, then one needs to perform an experimental exercise to test the value of candidate amino acids.  For a given organism, an amino acid may serve as a sole nitrogen source, sole carbon source, both as a carbon and nitrogen source, or as a building block for the synthesis of a protein, nucleic acid, or vitamin.  In addition, it must be ascertained as to the value of the amino acid with respect to nutritional needs to support catabolic and anabolic needs. For example, some fastidious bacteria, often paratrophs, can only utilize organic nitrogen sources.  For these bacteria, inorganic bound nitrogen would be useless.  On the other hand, many free-living bacteria are capable of utilizing amino nitrogen via. deamination, however, available ammonium ion will permit the bacteria to grow more efficiently, since they can assimilate ammonia nitrogen directly and not involve the energetic requirements of deaminases.  Again, you must conduct your own experiments to obtain information on the specific amino acids optimum for the growth of the microorganism of interest.  Studies of this sort are readily cited in the bacteriological literature.