Factors affecting biosurfactant production are divided into two: (a) environmental
and (b) nutritional (Moya et al. 2015; Gudina et al. 2015; Varjani and Upasani 2017).
Different element ratios, such as carbon:phosphorus, carbon:nitrogen, carbon:iron,
and carbon:magnesium, and optimization of these rates should be necessary to
achieve high production yield of biosurfactants (Gudina et al. 2015).
4.6.1 Carbon Sources
There are different carbon sources, such as starchy substrates, oils, animal fat,
petroleum effluents, lactic whey, olive oil mill effluent, plant-derived oils, distillery
wastes, molasses, vegetable oils and oil wastes, soap stock, and hydrophobic
mixtures (motor oil, crude oil, kerosene, diesel, paraffin), with great potential in
optimizing biosurfactant production (Abouseoud et al. 2008; Bezza and Chirwa
2015, 2017; Lee et al. 2018; Patowary et al. 2017). Pseudomonas aeruginosa yields a
better biosurfactant of 4.99 gL
À1 by utilizing the motor oil, 4.76 gL
À1 on
n-hexadecane (Joice and Parthasarathi 2014), and 4.11 gL
À1 on diesel fuel (Jimoh
and Lin 2019a).
4.6.2 Nitrogen Sources
A variety of inorganic and organic nitrogen sources, such as yeast extract, NaNO 3,
KNO 3, NH 4 NO 3, and urea, are used in the production of biosurfactants. The choosing organic over inorganic nitrogen source or the inverse depends on the microbial
strain or medium composition (Elazzazy et al. 2015; Ghribi and Ellouze-Chaabouni
2011). Maximum production of biosurfactants from Virgibacillus salarius was
reported when yeast extract was used as a nitrogen source (Hu et al. 2015).
4.6.3 Carbon:Nitrogen Ratio
Excessive nitrogen limits the buildup of products and leads to the synthesis of
cellular material. In contrast, high C:N ratios (i.e., low nitrogen levels), favoring
cell metabolism toward the production of metabolites, limit bacterial growth (Xia
et al. 2012). The presence of diesel fuel:(NH4) 2 SO 4 ratio of 3:1 resulted in a high
yield of biosurfactant production (3.79 gL
À1 ) with surface tension reduction
(32.0 mNm
À1 ) and highest dry cell weight (0.35 gL
À1 ) (Jimoh and Lin 2019a).
4.6.4 Phosphate and Salinity Source
Phosphate is usually provided in the form of triphosphates to harness biosurfactants.
Maqsood and Jamal (2011) reported that the maximum concentration of
rhamnolipids is yielded when the gram-negative bacterium was cultivated under
14
K. Mulugeta et al.
and (b) nutritional (Moya et al. 2015; Gudina et al. 2015; Varjani and Upasani 2017).
Different element ratios, such as carbon:phosphorus, carbon:nitrogen, carbon:iron,
and carbon:magnesium, and optimization of these rates should be necessary to
achieve high production yield of biosurfactants (Gudina et al. 2015).
4.6.1 Carbon Sources
There are different carbon sources, such as starchy substrates, oils, animal fat,
petroleum effluents, lactic whey, olive oil mill effluent, plant-derived oils, distillery
wastes, molasses, vegetable oils and oil wastes, soap stock, and hydrophobic
mixtures (motor oil, crude oil, kerosene, diesel, paraffin), with great potential in
optimizing biosurfactant production (Abouseoud et al. 2008; Bezza and Chirwa
2015, 2017; Lee et al. 2018; Patowary et al. 2017). Pseudomonas aeruginosa yields a
better biosurfactant of 4.99 gL
À1 by utilizing the motor oil, 4.76 gL
À1 on
n-hexadecane (Joice and Parthasarathi 2014), and 4.11 gL
À1 on diesel fuel (Jimoh
and Lin 2019a).
4.6.2 Nitrogen Sources
A variety of inorganic and organic nitrogen sources, such as yeast extract, NaNO 3,
KNO 3, NH 4 NO 3, and urea, are used in the production of biosurfactants. The choosing organic over inorganic nitrogen source or the inverse depends on the microbial
strain or medium composition (Elazzazy et al. 2015; Ghribi and Ellouze-Chaabouni
2011). Maximum production of biosurfactants from Virgibacillus salarius was
reported when yeast extract was used as a nitrogen source (Hu et al. 2015).
4.6.3 Carbon:Nitrogen Ratio
Excessive nitrogen limits the buildup of products and leads to the synthesis of
cellular material. In contrast, high C:N ratios (i.e., low nitrogen levels), favoring
cell metabolism toward the production of metabolites, limit bacterial growth (Xia
et al. 2012). The presence of diesel fuel:(NH4) 2 SO 4 ratio of 3:1 resulted in a high
yield of biosurfactant production (3.79 gL
À1 ) with surface tension reduction
(32.0 mNm
À1 ) and highest dry cell weight (0.35 gL
À1 ) (Jimoh and Lin 2019a).
4.6.4 Phosphate and Salinity Source
Phosphate is usually provided in the form of triphosphates to harness biosurfactants.
Maqsood and Jamal (2011) reported that the maximum concentration of
rhamnolipids is yielded when the gram-negative bacterium was cultivated under
14
K. Mulugeta et al.