Fed-batch production of citric acid by Candida lipolytica grown on n-paraffins

Large-Scale Production of Isocitric Acid Using Yarrowia lipolytica Yeast with Further Down-Stream Purification

Isocitric acid (ICA) refers to a group of promising regulators of energy metabolism which has antistress, antihypoxic, and antioxidant activities. In this paper, we reported a process of ICA production from rapeseed oil using yeast Yarrowia lipolytica VKM Y-2373 in a 500-L fermentor. The producer synthesized 64.1 g/L ICA with a product yield of 0.72 g/g and a productivity 0.54 g/L·h. We also developed an effective purification method, including a cell separation, clarification, concentration, acidification, and crystallization process, which resulted in the formation of the crystals of monopotassium salt of ICA with a purity of 99.0–99.9%. To the best of our knowledge, this is the first report on an ICA production process at an upscaled bioreactor level.

Modelling of the Citric Acid Production from Crude Glycerol by Wild-Type Yarrowia lipolytica DSM 8218 Using Response Surface Methodology (RSM)

Crude glycerol is the main by-product of the biodiesel manufacturing industry (10% w/w). Its use as a substrate in microbial fermentations is a concrete strategy to efficiently address its market surplus. In this study, the conversion of crude glycerol to citric acid, a key biochemical in the emerging bioeconomy, by a wild-type yeast Yarrowia lipolytica DSM 8218 was modelled using the Response Surface Methodology. The model relates C/N mass ratio and crude glycerol concentration to maximize the citric acid yield in flask scale using two different N sources, yeast extract and ammonium sulphate. Under the optimal conditions (yeast extract, C/N 141, glycerol 33 g/L), the conversion yield was 0.249 g/g. The optimal conditions were used for up-scaling a fed-batch fermentation in a 2 L bioreactor highlighting a metabolic shift from mannitol to citric acid when high stirring rates were applied (800 rpm). In these conditions, a morphic transition from pseudo-mycelial form to round-shaped yeast-like cells was observed too.

Citric Acid Production of Yeasts: An Overview

Background

Citric acid, an intermediate product of the Krebs cycle, has a wide usage area in the food industry since it has some functions such as acidulant, flavouring agent, preservative and antioxidant. Although molds are the most commonly used microorganisms in the citric acid production, it is known that there are significant advantages of using yeasts.

Purpose and scope

The microbial citric acid production mechanism needs to be well understood to make production more efficient. In this study, the yeasts used in the production, fermentation types and the factors affecting production were reviewed with studies.

Methodology

Although production of citric acid can be produced by chemical synthesis, the fermentation is preferred because of its low cost and ease of use. More than 90% of citric acid produced in the world is obtained by fermentation.

Results

Yarrowia lipolytica, Candida zeylanoides and Candida oleophila are evaluated for citric acid production with substrates such as molasses, glucose, sucrose and glycerol. On the other hand, there is great interest in developing processes with new substrates and/ or microorganisms.

Conclusion

Although the microbial strain is an important factor, the factors such as carbon, phosphorus and nitrogen sources, aeration, the presence of trace elements and pH are also parameters affecting the production.

Citric Acid Production by Aspergillus niger Cultivated on Parkia biglobosa Fruit Pulp

The study was conducted to investigate the potential of Parkia biglobosa fruit pulp as substrate for citric acid production by Aspergillus niger. Reducing sugar was estimated by 3,5-dinitrosalicylic acid and citric acid was estimated spectrophotometrically using pyridine-acetic anhydride methods. The studies revealed that production parameters (pH, inoculum size, substrate concentration, incubation temperature, and fermentation period) had profound effect on the amount of citric acid produced. The maximum yield was obtained at the pH of 2 with citric acid of 1.15 g/L and reducing sugar content of 0.541 mMol(-1), 3% vegetative inoculum size with citric acid yield of 0.53 g/L and reducing sugar content of 8.87 mMol(-1), 2% of the substrate concentration with citric acid yield of 0.83 g/L and reducing sugar content of 9.36 mMol(-1), incubation temperature of 55°C with citric acid yield of 0.62 g/L and reducing sugar content of 8.37 mMol(-1), and fermentation period of 5 days with citric acid yield of 0.61 g/L and reducing sugar content of 3.70 mMol(-1). The results of this study are encouraging and suggest that Parkia biglobosa pulp can be harnessed at low concentration for large scale citric acid production.

Raw Glycerol as Substrate for the Production of Yeast Biomass

Abstract: The possibility of using raw glycerol as a substrate for yeast biomass production as a source of proteins was investigated. Biomass concentration, protein content and total protein content of four yeasts (Yarrowia lipolytica NRRL YB-423, Candida lipolytica NRRL Y-1095, Candida utilis NRRL Y-900 and Candida rugosa NRRL Y-95) were determinate, comparing analytical grade glycerol and raw glycerol. Y. lipolytica NRRL YB-423 has been selected as promising for cultivation in a raw glycerol-based medium, mainly due to the higher biomass concentration in relation to the other strains. For this strain, four different culture media were tested. The best results were obtained with 50 g/L glycerol, 5.5 g/L ammonium phosphate, 5.5 potassium dihydrogen phosphate, 1 g/L ammonium sulphate, 0.25 g/L magnesium sulphate, 0.021 g/L calcium chloride dehydrate, 1 g/L yeast extract, 1 g/L peptone, pH adjusted to 5.5. In these conditions, it was possible to obtain 17.8 ± 0.6 g/L maximum biomass concentration, 18.2 ± 1.0% protein content and 3.1 ± 0.1 g/L total protein production. These results represent a 1.2-fold increase in biomass concentration, a 1.5-fold increase in protein content and a 1.9-fold increase in total protein production in relation to the results obtained with the previously medium composition.

Effect of agitation and aeration on the citric acid production by Yarrowia lipolytica grown on glycerol

The effects of agitation rates from 400 to 900 rpm and aeration rates ranging from 0.18 to 0.6 vvm on biomass and citric acid production on glycerol media by acetate-negative mutants of Yarrowia lipolytica, Wratislavia 1.31 and Wratislavia AWG7, in batch culture were studied. The agitation rates of 800 and 900 rpm (at a constant aeration rate of 0.36 vvm) and aeration rates within the range of 0.24-0.48 vvm (at a constant agitation rate of 800 rpm), which generated dissolved oxygen concentration (DO) higher than 40%, were found the best for citric acid biosynthesis from glycerol. An increase in agitation rate (higher than 800 rpm) and aeration rate (higher than 0.36 vvm) had no impact on DO and citric acid production. The highest citric acid concentration (92.8 g/L) and yield (0.63 g/g) were obtained with Wratislavia 1.31 strain at 0.24 vvm. The highest volumetric citric acid production rate (1.15 g/Lh) and specific citric acid production rate (0.071 g/gh) were reached at 0.48 vvm.

Biotechnological potential of inulin for bioprocesses

Inulin consists of linear chains of β-2,1-linked D-fructofuranose molecules terminated by a glucose residue through a sucrose-type linkage at the reducing end. In this review article, inulin and its applications in bioprocesses are overviewed. The tubers of many plants, such as Jerusalem artichoke, chicory, dahlia, and yacon contain a large amount of inulin. Inulin can be actively hydrolyzed by microbial inulinases to produce fructose, glucose and inulooligosaccharides (IOS). The fructose and glucose formed can be further transformed into ethanol, single-cell protein, single cell oil and other useful products by different microorganisms. IOS formed have many functions. Therefore, inulin can be widely used in food, feed, pharmaceutical, chemical and biofuels industries.