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Microbial gums are of great interest across many industries since they can be produced in large quantities, and research into several variations in the methods of production has led to economically viable alternatives. Xanthan gum, a widely used microbial gum, is industrially produced using glucose or invert sugars in batch fermentation mode. The culture conditions for xanthan production include maintaining a temperature between 28 and 30 °C, pH~7.0, and aeration rate higher than 0.3 (v/v), which is carried out for 100 hours [10]. Industrial grade xanthan is obtained by downstream processing that involves sterilization of the fermentation broth to kill the bacterial cells and to deactivate any enzymes. Cells are separated from the broth by centrifugation, and the cell‐free supernatant (CFS) is subjected to alcohol precipitation. The precipitated xanthan gum is either reprecipitated or spray‐dried and subsequently milled to the desired size [11]. Pullulan, another important microbial gum, is industrially produced similarly to xanthan gum. For the production of pullulan, liquefied starch is used as carbon source, and culture conditions include a temperature of 30 °C, pH~6.5 in aerated conditions for 100 hours to obtain the maximum pullulan yield of around 70% of the substrate used [5]. Other microbial gums like dextran can also be purified from CFS using ethanol precipitation. However, an alternate method for dextran production is by using either CFS‐containing enzyme dextransucrase or separately purified dextransucrase. Dextransucrase is added to sucrose in a controlled reaction condition, which results in dextran of high purity [12].

Centrifugal packed‐bed reactor (CPBR) was used for the production of xanthan gum, where the bacterial cells were immobilized in the rotating fibrous matrix. The pumping and circulation of the media through the matrix ensured the cells having good liquid and gas transfer. This process resulted in good separation of xanthan and cells, and could lead to less energy‐consuming downstream processing [13].

The use of alternative substrates for microbial gum production has seen interest among researchers. Xanthan gum production by using hydrolyzed starch from rice, barley, and corn starch, as well as the use of acid whey, sugarcane molasses, waste sugar beet pulp, and peach pulp, have resulted in competitive yields but less than that of glucose [14]. Coconut milk as a substrate was used to produce pullulan, where 54g/l pullulan was produced in 36 hours of fermentation at 30 °C [15]. Cane molasses have been used to produce welan gum using sulfuric acid hydrolysis as pretreatment, which resulted in a high welan gum yield of 41 g/l. The resulted welan gum was found to have acceptable molecular weight and rheological properties with better thermal stability with control substrate glucose [16].