Page 243 - Lignocellulosic Biomass to Liquid Biofuels

Syngas fermentation to bioethanol 199

peptone (10.0 g/L), soluble starch (1.0 g/L), glucose (5.0 g/L), cysteine
hydrochloride (0.5 g/L), sodium chloride (5.0 g/L), sodium acetate
(3.0 g/L), and agar (0.5 g/L) mixed with deionized water at a ratio of
38 g/L [41]. The medium is needed to be sterilized by autoclaving at
121°C for 20 min. In addition, microorganisms are to be reactivated by
transferring 2 mL of the stock culture into 20 mL of RCM prior to culti-
vation. Subsequently, cultural serum bottle is cleaned with nitrogen (N 2 )
gas for 2 min to create anaerobic condition and inoculate at optimized
temperature.
The medium for syngas fermentation contains (g/L) mineral solution
(10 mL), trace element solution (10 mL), vitamin solution (10 mL),
peptone (2 g), yeast extract (1 g), L-cysteine-HCl (0.5 g), morpholinoetha-
nesulfonic acid (5 g), xylose (5 g), and resazurin (1 mL; 0.1%), which is
added as a redox potential indicator [41]. The pH of the medium has
been controlled as per fermentation process condition. The additional
nutrient is also needed for the experimental medium preparation.
• The mineral solution added to the medium (per liter): NaCl (80 g),
NH 4 Cl (100 g), KCl (10 g), KH 2 PO 4 (10 g), MgSO 4 7H 2 O (20 g),
and CaCl 2 2H 2 O (4 g).
• The trace element solution added to the medium (per liter): nitrilotriacetic
acid (2 g), MnCl 2 4H 2 O (1.3 g), CoCl 2 6H 2 O(0.2 g), ZnSO 4 7H 2 O
(0.2 g), FeCl 3 6H 2 O(0.4 g), CuCl 2 2H 2 O(0.02 g),NiCl 2 6H 2 O
(0.02 g), Na 2 MoO 4 2H 2 O (0.02 g), and Na 2 WO 4 2H 2 O (0.025 g).
The prepared fermentation medium is required to be autoclaved at
121°C for 20 min and cooled down to room temperature under the bio-
safety hood. Subsequently, the syngas is passed through the broth medium
through the specific types of bioreactor for the production of acetic acid
or bioethanol.

6.1.3 Microbial cultivation system
Following are the three main types for microbial growth cultivation
system:
1. batch cultivation,
2. fed-batch cultivation, and
3. continuous cultivation.
1. Batch cultivation: Batch culture is the closed system where there is no
interaction between system and surrounding during the experiments. In
this technique, fermentation broth medium is prepared initially and then