Citric acid production from sucrose by recombinant Yarrowia lipolytica using semicontinuous fermentation

Abstract

The genetically modified yeast strain Yarrowia lipolytica H222-S4(p67ICL1)T5 is able to utilize sucrose as a carbon source and to produce citric and isocitric acids in a more advantageous ratio as compared to its wild-type equivalent. In this study, the effect of pH of the fermentation broth (pH 6.0 and 7.0) and proteose-peptone addition on citric acid production by the recombinant yeast strain were investigated. It was found that the highest citric acid production occurred at pH 7.0 without any addition of proteose-peptone. Furthermore, two process strategies (fed-batch and repeated fed-batch) were tested for their applicability for use in citric acid production from sucrose by Y. lipolytica. Repeated fed-batch cultivation was found to be the most effective process strategy: in 3 days of cycle duration, approximately 80 g/L citric acid was produced, the yield was at least 0.57 g/g and the productivity was as much as 1.1 g/Lh. The selectivity of the bioprocess for citric acid was always higher than 90% from the very beginning of the fermentation due to the genetic modification, reaching values of up to 96.4% after 5 days of cycle duration.

Effect of Nitrogen Concentration on the Biosynthesis of Citric Acid, Protein, and Lipids in the Yeast Yarrowia lipolytica

“…CA was synthesized in the stationary growth phase when Y. lipolytica VKM Y-2373 was in nitrogen starvation ( Figure 1 ), which agrees with literature data on the acid production from glucose [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ] and other carbohydrates [ 22 , 23 , 24 , 25 ].…”

“…Taking all this into account, researchers pay attention to alternative methods of production of CA and its salts. In particular, it is well established that the yeast Yarrowia lipolytica grown under nitrogen deficiency and carbon excess is able to produce CA in great amounts from various substrates, such as glucose [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ], glycerol [ 18 , 19 , 20 , 21 ], sucrose [ 22 , 23 ], xylose [ 24 ], the mixture of glucose and fructose [ 25 ], ethanol [ 26 ], vegetable oils [ 27 , 28 ], and so on. The cultivation of Y. lipolytica is much easier than that of A. niger because the yeast is characterized by a high growth rate and resistance to salts, and various metal ions, as well as to wide ranges of pH and cultivation temperatures [ 17 , 29 , 30 , 31 ].…”

Glycerol conversion into a single cell oil by engineered Yarrowia lipolytica

“…In many cases, this yeast was reported to secrete significant quantities of citric acid (CA) instead of massive lipid accumulation when nitrogen limited media was employed. This was observed particularly in nitrogen limited media with hydrophilic carbon sources . On the other hand, when Y. lipolytica was grown in a media containing fats and oils considerable lipid accumulation was observed.…”

A Review on Citric Acid Production by Yarrowia lipolytica Yeast: Past and Present Challenges and Developments

“…The strain was subsequently assessed through repeated fed-batch and fed-batch modes for over 200 h. The most effective process was determined to be repeated fed-batch with a duration of 72 h, producing 57.7-114.5 g/L CA with a yield (Y CA ) of 0.49-0.64 g/g and a productivity (Q CA ) of 0.66-1.1 g/L•h. The selectivity of the process, which was initially 90% at the beginning of fermentation, increased to 96.4% after five cycles [131]. The manipulation of the Y. lipolytica SWJ-1b strain, through expression of INU1 and ICL1 genes and deletion of the ACL1 gene, generated transformant № 30, which possesses an enhanced acid-forming capacity (84 g/L CA; Y CA = 0.84 g/g and Q CA = 0.22 g/L•h) [135].…”