Maximum Citric Acid Production Research Articles

Investigating the Usefulness of Wild Dioscorea esculenta (Wild Yam) Flour as Substrate for Citric Acid Biosynthesis

Background and Objective: The cost of substrate represents a significant percentage of the total biosynthesis cost of citric acid. There is need to continue searching for better and cheap underutilize starchy raw material for citric acid biosynthesis. Therefore, the objective of this research was to biologically synthesis citric acid in submerged fermentation of Aspergillus niger using wild Dioscorea esculenta (wild yam) tubers.
 Methodology: Submerged fermentation was conducted and the effect of Dioscorea esculenta concentrations, combined pretreatment and membrane permeability induction on citric acid biosynthesis were carried out.
 Results: Citric acid concentration increased as the concentration of the wild yam increased with maximum citric acid production of 10.5 ± 0.9 g/ l after 96 hours of fermentation. The overnight combined pretreatment with 0.3 % NaOH before pretreatment at 121oC for 20 minutes as one time combined pretreatment yielded 15. 0 ±1.2 g/l citric acid. Calcium chloride membrane induction produced 24.5 ± 1.3 g/l citric acid concentration respectively after 96 hours of fermentation.
 Conclusion: The result showed that wild Dioscorea esculenta tubers can be used as a substrate for the biosynthesis of citric acid. The biosynthesis of citric acid from Dioscorea esculenta tubers was enhanced by increased in concentration, combined pretreatment and membrane permeability induction.

Comparison of three culture media for one-step and two-step bioleaching of nickel and cadmium from spent Ni-Cd batteries by Aspergillus niger

Among the biological processes, bioleaching is the most widely employed method for metal extraction from electronic waste (e-waste). The purpose of this research was to evaluate the ability of one-step and two-step bioleaching under different culture media for nickel (Ni) and cadmium (Cd) removed from spent Ni-Cd batteries by the fungus Aspergillus niger. In this result, the concentrations of Ni and Cd in battery scraps from e-waste recycling shops were respectively 578.13 ± 7.02 mg Ni g-1 and 128.35 ± 11.42 mg Cd g-1. During the bioleaching process, both heavy metal removals were higher in Richards’s Broth (RB) followed by the Potato Dextrose Broth (PDB) and Malt Extract Broth (MEB), respectively. The maximum citric acid production (96.99±3.05 mM) and lower pH values were obtained in the RB medium. The bioleaching experiment showed that the recovery for the two-step leaching method was higher than the one-step bioleaching method. Following an incubation period of 21 days between the spent Ni-Cd batteries and RB medium, the two-step bioleaching experiment suggested that the citric acid products of A. niger were the best leaching agent for Ni and Cd bioleaching.

Valorization of Banana Peel for Citric Acid Production under Solid State Fermentation with Aspergillus niger

Valorization of banana peel (BP) through solid state fermentation (SSF) was aimed<br /> in this research. The appropriate conditions of citric acid (CA) production by SSF of<br /> Aspergillus niger were investigated. Firstly, the optimum initial pH of the BP and the<br /> aeration rate were studied by conducting SSF in a 250-mL flask and 2-L glass column,<br /> respectively. It was found that the initial pH of the BP and aeration rates affected the CA<br /> production. The results showed that the initial pH of 5.0 and 1.0 vvm aeration were appropriate for the CA production of A. niger using BP as a substrate. The problem of rising temperature during SSF was found when applying the optimum condition to the SSF<br /> in the 20-L packed bed bioreactor (PBB), which caused a decrease in the CA production<br /> compared to that of the glass column. The cooling air jacket constructed to the PBB to<br /> remove the heat during the SSF helped increase the CA production from that in the PBB.<br /> The maximum CA production in the 20-L air-jacketed PBB was 124.0±19.2 mg g–1DS.

Production of Citric Acid by Trichoderma viride Isolated from Soil in Keffi, Nigeria Using Glucose Enhanced Substrates

Aim: This study was aimed at the production of citric acid by Trichoderma viride (T. viride) isolated from soil in keffi, Nigeria, using glucose enhanced substrate.
 Place and Duration of the Study: Department of Microbiology Faculty of Natural and Applied Sciences Nassarawa State University Keffi, Nigeria, between April and June 2017.
 Methodology: Trichoderma viride was isolated from soil in Keffi and identified using standard microbiology methods. Two types of glucose production media were prepared by following standard fermentation conditions. The citric acid produced was estimated using Gas Chromatography/Mass Spectrometry (GC/MS) method respectively.
 Results: The maximum citric acid production of 12.03±0.31g/l was obtained at pH 6.0 with glucose with soybeans cake by T. viride and on sugar concentration of 160 g/l 15.17±3.01 g/l. The fermentation broth containing glucose and soy beans cake has the highest production of citric acid on both fermentation parameters tested respectively.
 Conclusion: Different fermentation conditions such as pH and sugar concentration substrate enhanced on the production of citric acid. This study showed that pH 6.0 with glucose with soybeans cake has highest citric acid production and at sugar concentration of 160 g/l with glucose and soybeans cake produced the highest citric acid by T. viride.

Increase of Citric Acid Production by Aspergillus niger InaCC F539 in Sorghum's Juice Medium Amended with Methanol

ABSTRACT Citric acid demand increases steadily, and there is a need to increase productivity through selection of suitable carbon sources, and addition of substances that increase citric acids production rate. Methanol has been suggested to increase citric acid fermentation on high carbohydrate containing substances. The objective of the study was to evaluate the suitability of sweet sorghum juice for citric acids production and to verify the effect of methanol on citric acids production using Aspergillus niger InaCC F539 as inoculant. Sweet sorghum juice with the total initial reducing sugar of 11.5 % (w/v) was used as the sole carbon sources. To study the effect of total initial reducing sugar on citric acid production the initial reducing sugar was adjusted to the concentration of 30 to 75 g/L. Preliminary experiment was conducted to get the optimum methanol concentration that stimulate citric acid production. The optimum methanol concentration that stimulate citric acid production was 4% (v/v). Submerged fermentation was conducted as shake culture (125 rpm at 28 °C). Citric acids production was affected by total initial reducing sugar. Higher total initial reducing sugar produced higher citric acids. Maximum citric acid production was 18.96g/L on sweet sorghum juice with 75 g/L total initial reducing sugar. Methanol 4 % (v/v) increase citric acid production by 41.35 to 65.89 %. Juice of sweet sorghum was a good medium for citric acids production, and methanol stimulate and increase citric acid production. It is a good basis for exploring efficient and cost effective industrial scale citric acid production. Keywords: Citric acid, Methanol, Sweet sorghum, Aspergillus niger

Citric acid production using a biological electrodialysis with bipolar membrane

The aim of this study was to investigate the feasibility of citric acid (CA) production using a biological electrodialysis with bipolar membrane, i.e., the microbial electrolysis desalination and chemical-production cell (MEDCC). To optimize the performance, batch, recirculation, and packed ion-exchange resin (IER) modes were carried out in the MEDCC. With 0.1M Na3Cit, the maximum current density was 7.7±0.3, 9.2±0.6, and 11.1±0.5A/m2 in the batch, recirculation, and packed IER modes, respectively. The maximum CA production of 0.443±0.096M was achieved within 96h operation using 0.5M Na3Cit with the recirculation mode. The lowest internal resistance of 48.5Ω was observed with the packed IER mode. The lowest electric consumption of 0.81±0.03kWh/kg in the MEDCC was achieved with 0.5M Na3Cit and the recirculation mode, which was only 10–40% of the electrical energy consumed in other electrodialysis processes. The MEDCC with the recirculation mode had higher abundance of Geobacter and higher biomass in the anode biofim than that with the batch mode, resulting in better performance in terms of higher current density and CA production. The MEDCC should be a potential valuable method for CA production with low energy consumption.

Citric acid production from partly deproteinized whey under non-sterile culture conditions using immobilized cells of lactose—positive and cold-adapted Yarrowia lipolytica B9

The present study was performed to produce citric acid (CA) from partly deproteinized cheese whey (DPCW) under non-sterile culture conditions using immobilized cells of the cold-adapted and lactose-positive yeast Yarrowia lipolytica B9. DPCW was prepared using the temperature treatment of 90°C for 15min. Sodium alginate was used as entrapping agent for cell immobilization. Optimum conditions for the maximum CA production (33.3g/L) in non-sterile DPCW medium were the temperature of 20°C, pH 5.5, additional lactose concentration of 20g/L, sodium alginate concentration of 2%, number of 150 beads/100mL and incubation time of 120h. Similarly, maximum citric acid/isocitric acid (CA/ICA) ratio (6.79) could be reached under these optimal conditions. Additional nitrogen and phosphorus sources decreased CA concentration and CA/ICA ratio. Immobilized cells were reused in three continuous reaction cycles without any loss in the maximum CA concentration. The unique combination of low pH and temperature values as well as cell immobilization procedure could prevent undesired microbial contaminants during CA production. This is the first work on CA production by cold-adapted microorganisms under non-sterile culture conditions. Besides, CA production using a lactose-positive strain of the yeast Y. lipolytica was investigated for the first time in the present study.

Citric acid production from pre-treated sugarcane bagasse by Aspergillus niger under solid state fermentation

Citric acid is one of the important commercially produced organic acid. The aim of the present work was to study the utilization of pre-treated sugar cane bagasse for citric acid production using Aspergillus niger under solid state fermentation. The maximum value of citric acid was observed in acid treated substrate followed by urea and heat respectively. Fermentation conditions were also optimized and maximum production of citric acid occurred when the pH, Initial moisture content and temperature of the fermentation medium were 5, 65 per cent and 30°C, respectively. As a globally required organic acid for various industrial applications, citric acid can be produced at large scale by utilizing pre-treated agro residues such as sugarcane bagasse. Application of agro residues in the production of value added product can be a positive step towards agricultural waste management.

Optimization of Chemical Parameters for the Production of Citric acid using Box-Behnken Design

Statistical experimental design was employed for the improvement of citric acid production from Madhuca indica through submerged fermentation process using mutant fungi Aspergillus niger MTCC 282. Efficient production of citric acid by mutant Aspergillus niger MTCC 282 grown on a sugar rich byproduct requires the supplementation of the optimized quantities of nutrients. Optimization of chemical parameters for the production of citric acid was done by Box-Behnken design. Box-Behnken design was used to statistically compare different combinations of four different nutrients, namely Ammonium sulphate ((NH4)2SO4), Magnesium (Mg2+), Ethylene diamine tetra acetic acid (EDTA) and Potassium phosphate (KH2PO4), for the maximum production of citric acid. The optimum nutrient concentrations obtained using the Box-Behnken design were Ammonium sulphate ((NH4)2SO4) 0.2138 g/l, Magnesium (Mg2+) 0.1896 g/l, Ethylene diamine tetra acetic acid (EDTA) 0.3968 g/l and Potassium phosphate (KH2PO4)3 g/l. Under the optimum conditions, mutant Aspergillus niger MTCC 282 produced the maximum citric acid of 75 g/l of citric acid/ kg substrate at pH 4.

목질계 농부산물을 이용한 고체발효에서 발효조건 최적화를 통한 구연산 생산 증대

본 실험에서는 농부산물인 밀짚을 고체배지로 사용하여 Aspergillus niger NRRL 567에서 구연산 생산 시, 발효조건과 첨가제가 구연산 생산에 미치는 영향을 단일변수(one-factor-at-a-time) 최적화를 이용하여 주요 인자의 순차적 최적화를 수행하였다. 발효 72시간에서 온도, 수분함량, 입자크기, pH와 첨가제 농도를 최적화했을 때, 각각 <TEX>$30^{\circ}C$</TEX>, 70%, 0.5~1.0 mm, pH 5.5와 4% 메탄올 첨가조건에서 최대 구연산 생산인 206.0 g/kg 건조중량 (DM)을 확인할 수 있었다. 이는 최적화 이전 구연산 최고 생산인 74.5 g/kg DM 대비 177% 증가한 결과이다. 최적화 실험에서 도출된 조건을 밀짚, 옥수수대와 피트모스(peat moss)에 적용하여 고체발효를 수행하였을 때, 발효 120시간에서 각각 231.8, 213.8, 240.2 g/kg DM 구연산 생산을 확보하였다. 본 실험 결과는 밀짚과 옥수수대 등의 목질계 농부산물을 이용한 구연산 생산 시, 고체발효법이 기존의 액체발효법의 대체가 가능함을 시사하였다. The present study was carried out to evaluate the potential of lignocellulosic byproducts for the production of citric acid through solid-state fermentation by Aspergillus niger NRRL 567. A sequential optimization based on one-factor-at-a-time method was applied to optimize fermentation conditions and media constituents. The results obtained from the optimization indicated that <TEX>$30^{\circ}C$</TEX>, 70% moisture content, 0.5~1.0 mm particle size, pH 5.5 and 4% methanol were found to be the optimum condition at 72 hr fermentation. The application the optimization resulted in an improvement of maximum citric acid production from 74.5 to 206.0 g/kg dry material (DM) from wheat straw. The optimal condition was used to produce citric acid from A. niger grown on different lignocellulosic byproducts, including wheat straw, corn stover and peat moss. A. niger produced the highest citric acid levels of 231.8, 213.8 and 240.2 g/kg DM at 120 hr fermentation, respectively.

Optimization of citric acid production from a carrot juice-based medium by Yarrowia lipolytica using response surface methodology

In this study, diluted and fortified carrot juice was used for modelling and optimization of citric acid production by a new mutant strain, Yarrowia lipolytica K-168. Protein concentrate obtained from fine flour -a byproduct of semolina production- was used as a nitrogen source in the fermentation medium. Interactive effects of selected independent variables, initial total sugar concentration, initial pH, initial concentration of protein concentrate obtained from fine flour of semolina and temperature, on the growth and citric acid production of the yeast were investigated. An experimental design including 30 experiments was conducted by using the method of central composite design. Modelling the effects of these independent variables on maximum citric acid concentration, maximum citric acid production rate, citric acid yield, the ratio of maximum citric acid concentration to maximum isocitric acid concentration and specific growth rate were performed by response surface methodology. The variations of all of the responses with the independent variables were defined by a quadratic model. Numeric optimization was performed by using the desireability function. The conditions with 190.83 g/L initial sugar concentration, 5.90 initial pH, 0.07 g/L initial concentration of fine flour protein concentrate and 27.86 °C were determined as optimal conditions for citric acid production. The maximum citric acid concentration reached to 80.53 g/L in optimal conditions.

Production of citric and isocitric acid by Yarrowia lipolytica strains grown on different carbon sources

Objective: The goal of this study was to determine the influence of various carbon sources on the citric and isocitric acid production by various Yarrowia lipolytica strains. Methods: The yeasts used in our study were first investigated for organic acid production using screening media. Then, the effect of several complex carbon sources on the citric and isocitric acid production of selected yeast strains was investigated. The amount of citric and isocitric acid production was determined via enzymatic reactions. Results: In this study, 22 Y. lipolytica strains were investigated for the organic acid production. Among these strains, 2 strains (TEM YL 3 and TEM YL 20) were found to be highest organicacid producer. Taken all results together, the highest amounts of citric acid (66.2 g/L for TEM YL 3, 50.0 g/L for TEM YL 20) were observed in the production medium containing sunflower oil. Conclusion: Citric acid consumption, and thus, the need for it are constantly rising in our country, which imports citric acid. Therefore, in order to meet this need, further studies which will yield to the maximum citric acid production should be performed by utilizing waste carbon sources and by using new low-cost but high citric acid-producing strains.

Screening of agro‐industrial wastes for citric acid bioproduction by Aspergillus nigerNRRL 2001 through solid state fermentation

The citric acid (CA) industry is currently struggling to develop a sustainable and economical process owing to high substrate and energy costs. Increasing interest in the replacement of costly synthetic substrates by renewable waste biomass has fostered research on agro-industrial wastes and screening of raw materials for economical CA production. The food-processing industry generates substantial quantities of waste biomass that could be used as a valuable low-cost fermentation substrate. The present study evaluated the potential of different agro-industrial wastes, namely apple pomace (AP), brewer's spent grain, citrus waste and sphagnum peat moss, as substrates for solid state CA production using Aspergillus niger NRRL 2001. Among the four substrates, AP resulted in highest CA production of 61.06 ± 1.9 g kg(-1) dry substrate (DS) after a 72 h incubation period. Based on the screening studies, AP was selected for optimisation studies through response surface methodology (RSM). Maximum CA production of 312.32 g kg(-1) DS was achieved at 75% (v/w) moisture and 3% (v/w) methanol after a 144 h incubation period. The validation of RSM-optimised parameters in plastic trays resulted in maximum CA production of 364.4 ± 4.50 g kg(-1) DS after a 120 h incubation period. The study demonstrated the potential of AP as a cheap substrate for higher CA production. This study contributes to knowledge about the future application of carbon rich agro-industrial wastes for their value addition to CA. It also offers economic and environmental benefits over traditional ways used to dispose off agro-industrial wastes.

고체발효에서 반응표면분석법을 이용한 구연산 생산 최적화

본 실험에서는 Aspergillus niger NRRL 567의 고체배양을 이용한 구연산 생산 시, 물리/화학적 발효 조건인 배양 온도, 배지 pH, 접종 농도 및 수분 함량이 구연산 생산에 미치는 영향을 단일변수(one-factor-at-a-time)와 반응표면 분석법(surface response methodology)을 이용하여 순차적 최적화를 수행하였다. 단일변수 최적화의 경우, A. niger에 의한 구연산 생산은 물리/화학적 발효 조건에 의해 영향을 받으며, 발효 온도 <TEX>$30^{\circ}C$</TEX>, 영양 배지 pH 7.1, 수분 함량 75%와 접종 농도 <TEX>$4.0{\times}10^6$</TEX> spores/ml에서 최대 구연산 생산인 98.2 g/kg DPM (dry peat moss)을 보였다. 단일변수 최적화에 근거하여 반응표면 분석법을 도입하여 2차 최적화를 수행했을 경우, 배지 pH와 수분 함량이 구연산 생산에 유의한 영향을 주었으며 온도 <TEX>$26.5^{\circ}C$</TEX>, 영양 배지 pH 9.9, 수분 함량 75.1%와 접종 농도 <TEX>$6.0{\times}10^6$</TEX> spores/ml에서 최대 구연산 생산인 118.8 g/kg DPM가 얻어졌다. 이는 최적화 이전의 대조군에 비해 구연산 생산이 1.6배 증가한 결과이다. In this present study, Aspergillus niger NRRL 567 was cultivated on an inert support material and the effects of various fermentation parameters including temperature, nutrient solution pH, inoculation level, and moisture content were observed and optimized by one-factor-at-a-time (OFAT) and response surface methodology (RSM), sequentially. It was found that the incubation temperature of <TEX>$30^{\circ}C$</TEX> with 75% moisture content, nutrient solution pH of 7.1 and inoculation level of <TEX>$4.0{\times}10^6$</TEX> spores/ml were the most favorable. Again, fermentation parameters were optimized using RSM. The determined optimum condition is <TEX>$26.5^{\circ}C$</TEX>, pH 9.9, 75.1%, and <TEX>$6.0{\times}10^6$</TEX> spores/ml. Under this optimized condition, A. niger NRRL 567 produced 118.8 g citric acid/kg dry peat moss at 72 hr. Maximum citric acid production of optimized condition by RSM represented a 1.6-fold increase compared to that obtained from control experiment.

Citric acid production from Aspergillus niger MT-4 using hydrolysate extract of the insect Locusta migratoria

Citric acid (CA) is the most important organic acid used in the food and other industries. Locusta migratoria is an insect species, which has rich nutritional composition (especially protein) and cultivated in some countries. Therefore, the present study investigated the usability of hydrolysate extract of L. migratoria biomass as substrate for the production of CA from Aspergillus niger MT-4. The insect extract (IE) was found to be rich in ash (34.9g/100g), protein (35.6g/100g) and mineral contents. Yeast extract was found to be the most favorable substrate for biomass production, whereas the maximum production of CA (41.8g/L) was achieved in the medium containing IE. Besides, uniform pellets with the smallest size (4mm) were observed in IE medium. It was thought that rich magnesium (6.78g/100g) and manganese (1.14g/100g) contents of IE increased the production of CA, resulting in the formation of small uniform pellets. This is the first report on the effect of protein-rich insect biomasses on the production of CA. In this regard, L. migratoria biomass was tested for the first time as a CA-production substrate.

Optimization of date syrup for enhancement of the production of citric acid using immobilized cells of Aspergillus niger

Date syrup as an economical source of carbohydrates and immobilized Aspergillus niger J4, which was entrapped in calcium alginate pellets, were employed for enhancing the production of citric acid. Maximum production was achieved by pre-treating date syrup with 1.5% tricalcium phosphate to remove heavy metals. The production of citric acid using a pretreated medium was 38.87% higher than an untreated one that consumed sugar. The appropriate presence of nitrogen, phosphate and magnesium appeared to be important in order for citric acid to accumulate. The production of citric acid and the consumed sugar was higher when using 0.1% ammonium nitrate as the best source of nitrogen. The production of citric acid increased significantly when 0.1g/l of KH2PO4 was added to the medium of date syrup. The addition of magnesium sulfate at the rate of 0.20g/l had a stimulating effect on the production of citric acid. Maximum production of citric acid was obtained when calcium chloride was absent. One of the most important benefits of immobilized cells is their ability and stability to produce citric acid under a repeated batch culture. Over four repeated batches, the production of citric acid production was maintained for 24days when each cycle continued for 144h. The results obtained in the repeated batch cultivation using date syrup confirmed that date syrup could be used as a medium for the industrial production of citric acid.

Effect of Particle Size on Production of Citric Acid from Oil Palm Empty Fruit Bunches as New Substrate by Wild Aspergillus niger

An investigation was carried out to evaluate the effect of different particle size of oil palm Empty Fruit Bunches (EFB) and their distribution as new substrate for the production of citric acid through Solid State Bioconversion (SSB) in laboratory scale by Aspergillus niger. The experiment was carried out to observe the productivity of citric acid with different particle size of EFB in 250 mL Erlenmeyer flasks. The result obtained through this study showed that the 0.5 mm down graded particle of EFB gave the highest production of citric acid compared to other particle size. The maximum production of citric acid of 131.3 g kg-1-EFB with the production rate of 16.4 g kg-1-day was obtained from EFB with particle size of 0.5 mm after 8 days of bioconversion. Furthermore, the results of particle size distribution show that the well-graded particle size of EFB produced the highest citric acid compared to uniformly-graded and gap-graded particle.

Use of nitrous acid mutant of Aspergillus niger for citric acid production from local cane-molasses

In this study, the enhancement of citric acid production from local molasses was attempted by mutagenesis. A local stain of Aspergillus niger was isolated from lemon leaves and treated with nitrous acid. The obtained mutant and the wild type ofA. niger were separately used for the bioconversion of the local molasses into citric acid. The molasses fermentation was carried out at 30°C in a stirred flask. The results showed that the mutant exhibited an increased efficiency for citric acid production when compared with the wild type. It produced 230.45 gl-1 of citric acid; two fold increase over the parent strain (105.67 gl-1), with higher sugar consumption by the mutant compared with the wild type. The maximum citric acid production levels were reached on the 9th day of fermentation by the mutant and the 10th day of fermentation by the wild strain. The mutant proved to be appropriate for citric acid production and waste material valorization in Rwanda. Also, this investigation showed itself to be one of ecofriendly technologies for Rwanda. So, the use of this technology should have impact on both the Rwanda economic development and environmental protection. Key words: Rwanda, Aspergillus niger, bioconversion, cane-molasses, citric acid, mutagenesis, mutant, nitrous acid.

Citric acid production by Koji fermentation using banana peel as a novel substrate

The growing demand for citric acid and the current need for alternative sources have encouraged biotechnologists to search for novel and economical substrates. Koji fermentation was conducted using the peels of banana ( Musa acuminata) as an inexpensive substrate for the production of citric acid using Aspergillus niger. Various crucial parameters that affect citric acid production such as moisture content, temperature, pH, inoculum level and incubation time were quantified. Moisture (70%), 28 °C temperature, an initial pH 3, 10 8 spores/ml as inoculum and 72 h incubation was found to be suitable for maximum citric acid production by A. niger using banana peel as a substrate.

Optimization of citric acid production by Aspergillus niger NRRL 567 grown in a column bioreactor

Citric acid production using Aspergillus niger NRRL 567 grown on peat moss has been optimized in a column bioreactor using a statistically based method. A 23 full factorial design with eight fermentation conditions was applied to evaluate significance on citric acid production and their interactions between variables, where the three independent variables evaluated were aeration rate, bed depth and temperature. Aeration rate and fermentation temperature were identified to be significant variables. Citric acid production markedly increases with aeration rate and fermentation temperature; however, the bed depth of solid substrate showed an insignificant effect on citric acid production. The optimum fermentation condition for citric acid production in a column bioreactor consisted of aeration rate of 0.84 vvm, bed depth of 22 cm and fermentation temperature of 32 °C. Under a given condition, a maximum citric acid production of 120.6 g/l was predicted and matched well with the experimental value of 123.9 g/kg.