Carbon partitioning into sorbitol,sucrose, and starch in source and sink apple leaves as affected by elevated CO2

Experiments were conducted in controlled growth chambers to evaluate how increases in CO₂ concentration ([CO₂]) affected carbon metabolism and partitioning into sorbitol, sucrose, and starch in various ages of apple leaves. Apple plants (Malus domestica), 1 year old, were exposed to [CO₂] of 200, 360, 700, 1000, and 1600 μl l⁻¹ up to 8 days. Six groups of leaves (counted from the shoot apex): leaves 1–5 (sink), 6–7 (sink to source transition), 8–9 (sink to source transition), 10–11 (nearly-matured source), 21–22 (mid-age source), and 30–32 (aged source), were sampled at 1, 2, 4, and 8 days after [CO₂] treatments for carbohydrate analysis. Increases in [CO₂] from a sub-ambient (200 μl l⁻¹) to an ambient level (360 μl l⁻¹) significantly increased the concentrations of sorbitol, sucrose, glucose, and fructose tested in all ages of leaves. Continuous increase in [CO₂] from ambient to super-ambient levels up to 1600 μl l⁻¹ also increased sorbitol concentration by ≈50% in source leaves, but not in sink and sink to source transition leaves. Increases in [CO₂] from 360 to 1600 μl l⁻¹, however, had little effect on sucrose content in all ages of leaves. Starch concentrations increased in all ages of leaves as [CO₂] increased. Rapid starch increases (e.g. 5-, 6-, 20-, and 50-fold increases for leaf groups 1–5, 6–7, 10–11, and 21–22, respectively) occurred from 700 to 1600 μl l⁻¹ [CO₂] during which increases in sorbitol concentration either ceased or slowed down. Our results indicate that changes in carbohydrates were much more responsive to CO₂ enrichment in source leaves than in sink and sink to source transition leaves. Carbon partitioning was favored into starch and sorbitol over sucrose in all ages of leaves when [CO₂] was increased from 200 to 700 μl l⁻¹, and was favored into starch over sorbitol from 700 to 1600 μl l⁻¹ [CO₂].     

Influence of the concentrations of d-xylose and yeast extract on ethanol production by Pachysolen tannophilus

To determine the most favorable conditions for the production of ethanol by Pachysolen tannophilus, this yeast was grown in batch cultures with various initial concentrations of two of the constituents of the culture medium: d-xylose (s_o), ranging from 1 g·l⁻¹ to 200 g·l⁻¹, and yeast extract (l_o), ranging from 0 g·l⁻¹ to 8 g·l⁻¹. The most favorable conditions proved to be initial concentrations of S_o=25 g·l⁻¹ and l_o=4 g·l⁻¹, which gave a maximum specific growth rate of 0.26 h⁻¹, biomass productivity of 0.023 g·l⁻¹·h⁻¹, overall biomass yield of 0.094 g·g⁻¹, specific xylose-uptake rate (q_s) of 0.3 g·g⁻¹·h⁻¹ (for t=50 h), specific ethanol-production rate (q_E) of 0.065 g·g⁻¹·h⁻¹ and overall ethanol yield of 0.34 g·g⁻¹; q_s values decreased after the exponential growth phase while q_E remained practically constant.     

Prodigiosin formation by Serratia marcescens in a chemostat

In a study of the control of metabolite formation, prodigiosin production by Serratia marcescens was used as a model. Specific production rates of prodigiosin formation were determined using batch culture technique. Sucrose as carbon source and NH₄NO₃ as nitrogen source resulted in a specific production rate of 0.476 mg prodigiosin (g cell dry weight)⁻¹ h⁻¹. Prodigiosin formation and productivity was inversely correlated to growth rate when the bacterium was grown under carbon limitation on a defined medium in a chemostat culture. The maximum specific growth rate (μ_max) was 0.54 h⁻¹ and prodigiosin was formed in amounts over 1 mg l⁻¹ up to a growth rate (μ) of 0.3 h⁻¹ at steady state conditions. At a dilution rate of 0.1 h⁻¹ growth at steady state with carbon and phosphate limitation supported prodigiosin formation giving a similar specific yield [1.17 mg prodigiosin (g cell dry weight)⁻¹ and 0.94 mg g⁻¹, respectively], however, cells grown with nitrogen limitation [(NH₄)₂SO₄] did not form prodigiosin. Productivity in batch culture was 1.33 mg l⁻¹ h⁻¹ as compared to 0.57 mg l⁻¹ h⁻¹ in the chemostat.     

Influence of pH on methane and sulfide production from methanol

To investigate the influence of pH on methane and sulfide production, continuous cultures were done using a bio-reactor packed with pumice stone. Sulfate (1 g SO₄²⁻·l⁻¹) in a methanol defined medium (10 g·l⁻¹) was almost completely reduced to sulfide at pHs between 7.0 and 7.5 in methane fermentation, but at pHs between 6.2 and 6.8, sulfate reduction to sulfide was suppressed up to 40%. In addition, methane fermentation was not inhibited by 10 g sulfate·l⁻¹.     

Effects of feed sugar concentration on continuous ethanol fermentation of cheese whey powder solution (CWP)

Cheese whey powder (CWP) solution with different CWP or sugar concentrations was fermented to ethanol in a continuous fermenter using pure culture of Kluyveromyces marxianus (DSMZ 7239). Sugar concentration of the feed CWP solution varied between 55 and 200 g l⁻¹ while the hydraulic residence time (HRT) was kept constant at 54 h. Ethanol formation, sugar utilization and biomass formation were investigated as functions of the feed sugar concentration. Percent sugar utilization and biomass concentrations decreased and the effluent sugar concentration increased with increasing feed sugar concentrations especially for the feed sugar contents above 100 g l⁻¹. Ethanol concentration and productivity (DP) increased with increasing feed sugar up to 100 g l⁻¹ and then decreased with further increases in the feed sugar content. The highest ethanol concentration (3.7%, v v⁻¹) and productivity (0.54 gE l⁻¹ h⁻¹) were obtained with the feed sugar content of 100 g l⁻¹ or 125 g l⁻¹. The ethanol yield coefficient (Y_P/S) was also maximum (0.49 gE gS⁻¹) when the feed sugar was between 100 and 125 g l⁻¹. The growth yield coefficient (Y_X/S) decreased steadily from 0.123 to 0.063 gX gS⁻¹ when the feed sugar increased from 55 to 200 g l⁻¹ due to adverse effects of high sugar contents on yeast growth. The optimal feed sugar concentration maximizing the ethanol productivity and sugar utilization was between 100 and 125 g l⁻¹ under the specified experimental conditions.     

Microbial processes and bacterial populations associated to anaerobic treatment of sulfate-rich wastewater

A pilot-scale (1.2 m³) anaerobic sequencing batch biofilm reactor (ASBBR) containing mineral coal for biomass attachment was fed with sulfate-rich wastewater at increasing sulfate concentrations. Ethanol was used as the main organic source. Tested COD/sulfate ratios were of 1.8 and 1.5 for sulfate loading rates of 0.65–1.90 kgSO₄²⁻/cycle (48 h-cycle) or of 1.0 in the trial with 3.0 gSO₄²⁻ l⁻¹. Sulfate removal efficiencies observed in all trials were as high as 99%. Molecular inventories indicated a shift on the microbial composition and a decrease on species diversity with the increase of sulfate concentration. Beta-proteobacteria species affiliated with Aminomonas spp. and Thermanaerovibrio spp. predominated at 1.0 gSO₄²⁻ l⁻¹. At higher sulfate concentrations the predominant bacterial group was Delta-proteobacteria mainly Desulfovibrio spp. and Desulfomicrobium spp. at 2.0 gSO₄²⁻ l⁻¹, whereas Desulfurella spp. and Coprothermobacter spp. predominated at 3.0 gSO₄²⁻ l⁻¹. These organisms have been commonly associated with sulfate reduction producing acetate, sulfide and sulfur. Methanogenic archaea (Methanosaeta spp.) was found at 1.0 and 2.0 gSO₄²⁻ l⁻¹. Additionally, a simplified mathematical model was used to infer on metabolic pathways of the biomass involved in sulfate reduction.     

Factors affecting l-arginine production in the continuous culture of an l-arginine producer of Corynebacterium acetoacidophilum

The effects of culture conditions on l-arginine production by continuous culture were studied using a stable l-arginine hyperproducing strain of Corynebacterium aceto-acidophilum, SC-190. Strain SC-190 demonstrated a volumetric productivity of 35 g l⁻¹·h⁻¹ at a dilution rate of 0.083h⁻¹ and feeding sugar concentration of 8%, and a product yield of 29.2% at a dilution rate 0.021h⁻¹ and feeding sugar concentration of 15%. The corresponding values for fed-batch culture are 0.85 g·l⁻¹·h⁻¹ and 26%. However, the product yield decreased with an increase in the volumetric productivity. To achieve stable l-arginine production, aeration and agitation conditions sufficient to maintain an optimal level of redox potential (>−100 mV) were necessary. The addition of phosphate to the feeding medium led to a decrease in l-arginine production. It was confirmed in the steady state that growth and l-arginine formation were inhibited by a high concentration of l-arginine.     

Enzymatic hydrolysis of corncob and ethanol production from cellulosic hydrolysate

 Enzymatic hydrolysis of corncob and ethanol fermentation from cellulosic hydrolysate were investigated. After corncob was pretreated by 1% H₂SO₄ at 108 °C for 3 h, the cellulosic residue was hydrolyzed by cellulase from Trichoderma reesei ZU-02 and the hydrolysis yield was 67.5%. Poor cellobiase activity in T. reesei cellulase restricted the conversion of cellobiose to glucose, and the accumulation of cellobiose caused severe feedback inhibition to the activities of β-1,4-endoglucanase and β-1,4-exoglucanase in cellulase system. Supplementing cellobiase from Aspergillus niger ZU-07 greatly reduced the inhibitory effect caused by cellobiose, and the hydrolysis yield was improved to 83.9% with enhanced cellobiase activity of 6.5 CBU g⁻¹ substrate. Fed-batch hydrolysis process was started with a batch hydrolysis containing 100 g l⁻¹ substrate, with cellulosic residue added at 6 and 12 h twice to get a final substrate concentration of 200 g l⁻¹. After 60 h of reaction, the reducing sugar concentration reached 116.3 g l⁻¹ with a hydrolysis yield of 79.5%. Further fermentation of cellulosic hydrolysate containing 95.3 g l⁻¹ glucose was performed using Saccharomyces cerevisiae 316, and 45.7 g l⁻¹ ethanol was obtained within 18 h. The research results are meaningful in fuel ethanol production from agricultural residue instead of grain starch.     

Continuous high-ethanol fermentation from cane molasses by a flocculating yeast

Repeated-batch fermentation by a flocculating fusant, Saccharomyces cerevisiae HA 2, was done in a molasses medium that contained 20% (w/v) total sugar, at 30°C in an automatically controlled fermentor, and the effects of ethanol concentration on the specific growth rate and the specific production rate of ethanol were studied. Both the specific growth rate and the specific production rate of ethanol fell with increase of ethanol concentration, and there was a linear correlation between each rate and the concentration of thanol. The maximum specific growth rate (μ_max) and the maximum specific production rate of ethanol (q_max) were 0.12 h⁻¹ and 0.1 g ethanol/10⁹ cells·h, respectively. The specific growth rate and the specific production rate of ethanol fell to zero at ethanol concentration of 89 g/l and 95 g/l, respectively. The number of viable cells, calculated from the linear inhibition equation, was 1.3 × 10⁹ cells/ml for production of 85 g/l ethanol at a dilution rate (D₁) of 0.2 h⁻¹. Based on this estimation, a laboratory-scale continuous fermentation, using two fermentors in series, was done. In the second fermentor, 85 g/l ethanol was produced at a dilution rate (D₁) of 0.2 h⁻¹ by the active feedig of the fermented mash from the first fermentor into the second fermentor by pumping (hereafter called active feeding). To maintain the number of viable cells above 10⁹ cells/ml in the second fermentor, a active feeding ratio of more than 23% was required. Under these conditions, 81 g/l ethanol was produced in the second fermentor at a dilution rate (D_t) of 0.25 h⁻¹, and the high ethanol productivity of 20.3 g/l·h could be achieved. A bench-scale continuous fermentation, using two fermentors in series, with a active feeding ratio of 25% was done. An ethanol concentration of 84 g/l in the second fermentor at a dilution rate (D_t) of 0.25 h⁻¹ was achieved, just as it was in the laboratory-scale fermentation test.     

Mathematical analysis of trickling filter response to pentachlorophenol shock load

The response of a laboratory trickling filter to a step increase in pentachlorophenol (PCP) feed concentration was analyzed using continuous stirred tank (CSTR) and plug flow reactor (PFR) models. The CSTR model provided a slightly better fit to experimental data than the plug flow model when specific growth rate, μ, and PCP-degrading biomass concentration before the shock load, X₀, were variable parameters but was clearly superior when the mean residence time, τ, was added as a third parameter. The three-parameter CSTR model accurately represented six of seven concentration response curves corresponding to step increases in PCP feed concentration of 12–165 mg l⁻¹ and 20–150 mg l⁻¹. The continuing improvement in system response to repetitive 20–150 mg l⁻¹ shock loads was reflected by a monotonic increase in the optimal estimates of initial rate of biomass production.     

Evaluation of distant carbon sources in biosurfactant production by a gamma ray-induced Pseudomonas putida mutant

Pseudomonas putida 33 wild strain, subjected to gamma ray mutagenesis and designated as P. putida 300-B mutant was used as microbial rhamnolipid-producer by using distant carbon sources (viz. hydrocarbons, waste frying oils ‘WFOs’, vegetable oil refinery wastes and molasses) in the minimal media under shake flask conditions. The behavior of glucose as co-substrate and growth initiator was examined. The 300-B mutant strain showed its ability to grow on all the substrates tested and produced rhamnolipid surfactants to different extents however; soybean and corn WFOs were observed to be preferred carbon sources followed by kerosene and paraffin oils, respectively. The best cell biomass (3.5 g l⁻¹) and rhamnolipids yield (4.1 g l⁻¹) were obtained with soybean WFO as carbon source and glucose as growth initiator under fed-batch cultivation showing an optimum specific growth rate (μ) of 0.272 h⁻¹, specific product yield (q_p) of 0.318 g g⁻¹ h and volumetric productivity (P_V) of 0.024 g l⁻¹ h. The critical micelle concentration of its culture supernatant was observed to be 91 mg rhamnolipids l⁻¹ and surface tension as 31.2 mN m⁻¹.     

Continuous production of an antibiotic polypeptide (nisin) by Lactococcus lactis using a bioreactor coupled to a microfiltration module

The continuous production of nisin, an antibiotic polypeptide, by Lactococcus lactis in a bioreactor system coupled to a microfiltration module is described. Nisin productivity with respect to both cultivation time (ND) and the quantity of glucose consumed (ND/S_f) in continuous production was enhanced by maintaining a low concentration of lactic acid in the broth. A maximum ND of 7.80 × 10⁴ U·l⁻¹·h⁻¹ and ND/S_f of 5.20 × 10³ U·g⁻¹·h⁻¹ were obtained when the glucose concentration in the feed medium was 15 g/l. These values represent about 4.1- and 4.5-fold increases, respectively, over those obtained in batch culture.     

Forming nanoparticles of α-amylase and embedding them into solid surfaces

In the current work nanoparticles (NPs) of α-amylase were generated in an aqueous solution using high-intensity ultrasound, and were subsequently immobilized on polyethylene (PE) films, or polycarbonate (PC) plates, or on microscope glass slides. The α-amylase NPs coated on the solid surfaces have been characterized by ESEM, TEM, FTIR, XPS and AFM. The substrates immobilized with α-amylase were used for hydrolyzing soluble potato starch to maltose. The amount of enzyme introduced in the substrates, leaching properties, and the catalytic activity of the immobilized enzyme were compared. The catalytic activity of the amylase deposited on the three solid surfaces was compared to that of the same amount of free enzyme at different pHs and temperatures. α-Amylase coated on PE showed the best catalytic activity in all the examined parameters when compared to native amylase, especially at high temperatures. When immobilized on glass, α-amylase showed better activity than the native enzyme over all pH and temperature values studied. However, the immobilization on PC did not improve the enzyme activity at any pH and any temperature compared to the free amylase. The kinetic parameters, K_m and V_max were also calculated. The amylase coated PE showed the most favorable kinetic parameters (K_m = 5 g L⁻¹ and V_max = 5E−07 mol mL⁻¹ min⁻¹). In contrast, the anchored enzyme-PC exhibited unfavorable kinetic parameters (K_m = 16 g L⁻¹, V_max = 4.2E−07 mol mL⁻¹ min⁻¹). The corresponding values for amylase-glass were K_m = 7 g L⁻¹, V_max = 1.8E−07 mol mL⁻¹ min⁻¹, relative to those obtained for the free enzyme (K_m = 6.6 g L⁻¹, V_max = 3.3E−07 mol mL⁻¹ min⁻¹).     

Characteristics of granular methanogenic sludge grown on phenol synthetic medium and methanogenic fermentation of phenolic wastewater in a UASB reactor

The growth of granules on a phenol synthetic medium and the methanogenic fermentation of industrial phenolic wastewater from a steel factory in an upflow anaerobic sludge blanket (UASB) reactor were investigated. Total granular sludge concentration retained in the UASB reactor was 6.7 g MLSS/l (6.0 g MLVSS/l) during the 10 months' operation on the phenol synthetic medium. This realized a maximum phenol removal rate of 2.2 g/l·d (phenol concentration of influent = 500 mg/l), which corresponded to 5.2 g COD/l·d at space velocity (SV) of 4.4 d⁻¹. The granules formed were of relatively small size ranging from 0.61 to 0.77 mm, and had a relatively low density of 0.013–0.023 g MLVSS/cm³ and low specific gravity (1.11) due to very low ash content (8.7–11.9%). Electron microscopic analysis showed that Methanothrix spp. appeared dominantly on the granule surface as well as within it. The specific metabolic activities of bacterial trophic groups were the highest for H₂ followed by acetate, benzoate, phenol, and propionate. In the case of industrial phenolic wastewater, although phenol efficiency was only 50% at SV of 0.4 d⁻¹, when the wastewater was diluted twofold and the treated wastewater was recycled at SV of 7.3 d⁻¹, the removal efficiencies of phenol and CODcr were restored to 90% (influent=400 mg/l) and 80% (influent=5,000 mg/l), respectively. It was suggested that recycling of the treated wastewater might be improved by partly degrading unknown toxic compounds contained in phenolic wastewater.     

Phosphate limitation stress induces xylitol overproduction by Debaryomyces hansenii

The physiological responses of xylose-grown Debaryomyces hansenii were studied under different nutritive stress conditions using continuous cultivation at a constant dilution rate of 0.055 h⁻¹. Metabolic steady-state data were obtained for xylose, ammonium, potassium, phosphate and oxygen limitation. For xylose and potassium limitation, fully oxidative metabolism occurred leading to the production of biomass and CO₂ as the only metabolic products. However, potassium-limiting cultivation was the most severe nutritional stress of all tested, exhibiting the highest xylose and O₂ specific consumption rates along with the lowest biomass yield, 0.22 g g⁻¹ xylose. It is suggested that carbon was mainly channelled to meet the cellular energy requirements for potassium uptake. For the other limiting nutritional conditions increasing amounts of extracellular xylitol were found for ammonium, phosphate and oxygen limitation. Although xylitol excretion is not significant for ammonium limitation, the same is not true for phosphate limitation where the xylitol productivity reached 0.10 g l⁻¹ h⁻¹, about half of that found under oxygen-limiting conditions, 0.21 g l⁻¹ h⁻¹. This work is the first evidence that xylitol production by D. hansenii might not only be a consequence of a redox imbalance usually attained under semi-aerobic conditions, but additional physiological mechanisms must be involved, especially under phosphate limitation. Cell yields changed drastically as a function of the limiting nutrient, being 0.22, 0.29, and 0.39 g g⁻¹ xylose for potassium, oxygen and phosphate limitation, respectively, and are a good indicator of the severity of nutritive stress.     

Effect of oxygen supply and dilution rate on the production of 2,3-butanediol in continuous bioreactor by Klebsiella pneumoniae

Kinetics of 2,3-butanediol production by Klebsiella pneumoniae (NRRL B199) from glucose have been studied in a continuous bioreactor. The effect of oxygen supply rate and dilution rate on the product output rate and yield of 2,3-butanediol were investigated. For a feed glucose concentration of 100 g l⁻¹, the optimum oxygen transfer rate is between 25.0–35.0 mmol l⁻¹ h⁻¹. Under these conditions, maximum product concentration obtained was 35 g l⁻¹ at a dilution rate of 0.1 h⁻¹ and the maximum product output rate obtained was 4.25 g l⁻¹ h⁻¹. The product yield based on the substrate utilized approached the theoretical value (50%) at low values of oxygen transfer rate but decreased with increasing oxygen transfer rate.     

Continuous ethanol production from raw starch using a reversibly soluble-autoprecipitating amylase and flocculating yeast cells

Direct ethanol production from raw starch was performed continuously using a combination of a reversibly soluble-autoprecipitating amylase (D-AS) in which Dabiase K-27 was immobilized covalently on an enteric coating polymer (hydroxypropyl methylcellulose acetate succinate, AS) as a carrier, and a flocculating yeast. Continuous production was carried out using a reactor equipped with a mixing vessel and a separation vessel. D-AS and the yeast were separated continuously from the product solution by self-sedimentation in the separation vessel and they were utilized repeatedly. In the continuous saccharification of raw starch by D-AS alone, the glucose productivity was about 3.6 g/l/h at a dilution rate (D) of 0.1 h⁻¹. In the continuous ethanol production from raw starch by a combination of D-AS and flocculating yeast cells, high ethanol productivity up to 2.0 g/l/h was achieved at D=0.1 h⁻¹. Although the enzymatic activity of D-AS is inactivated due to insolubilization of the enzyme by the accumulation of NaCl produced in controlling the pH in the reactor, it is possible to recover the D-AS enzymatic activity by removing the NaCl. This continuous fermentation system suggests a potential for effective ethanol production from raw starch, and it may be widely applicable in heterogeneous culture systems using solid substrates other than raw starch.     

Production of a new exopolysaccharide (EPS) by Pseudomonas oleovorans NRRL B-14682 grown on glycerol

Pure glycerol and glycerol-rich product (GRP) obtained from the biodiesel industries were used as carbon source for the production of a new extracellular polysaccharide (EPS) by Pseudomonas oleovorans NRRL B-14682. The influence of temperature (20–40 °C) and pH (6.0–8.0) was studied. A temperature of 30 °C and pH control at 6.8 gave the maximum cell growth and EPS production. The culture attained a maximum cell dry weight (CDW) of 9.55 g l⁻¹ and an EPS concentration of 11.82 g l⁻¹ when cultivated with pure glycerol. GRP was a suitable carbon source, as shown by the slightly higher EPS concentration (12.18 g l⁻¹). The EPS productivity obtained with GRP (3.85 g l⁻¹ d⁻¹) was almost twice that obtained with pure glycerol (2.00 g l⁻¹ d⁻¹). Also, the yield on glycerol was higher for the cultivation with GRP (0.36 g g⁻¹) than for pure glycerol (0.28 g g⁻¹). The EPS was a high molecular weight heteropolysaccharide, composed by neutral sugars (37–80 wt% galactose, 2–30 wt% glucose, 0.5–25 wt% mannose and 0.5–20 wt% rhamnose) and containing acyl group substituents (pyruvil, acetyl and succinyl were identified). The EPS forms highly viscous aqueous dispersions with many potential commercial applications.     

Ethanol production by whole cell immobilization using lignocellulosic materials as solid matrix

Amongst four carriers used, rice-straw was found to be superior in terms of ethanol production. The maximum productivity (17.84 gl⁻¹ h⁻¹) corresponded to a dilution rate of 0.39 h⁻¹, the ethanol concentration being 45.80 gl⁻¹. A multistage rhomboidal bioreactor was found to partially overcome the disruption effect caused by the generation of a large volume of carbon dioxide in the column. Increases in productivity of about 12.55% and 3.6%, respectively, were achieved using rhomboidal and tapered bioreactors as compared to the cylindrical bioreactor. It was observed that the generation time of cells, in both the immobilized and free states, was around 2.5 h. The ethanol yield (Y_p/s) in the lower part of the reactor was less in comparison with other zones, where the substrate utilization efficiency was relatively higher.     

Over-production of human interferon-γ by HCDC of recombinant Escherichia coli

A simple fed-batch process was developed using a modified variable specific growth rate feeding strategy for high cell density cultivation of Escherichia coli BL21 (DE3) expressing human interferon-gamma (hIFN-γ). The feeding rate was adjusted to achieve the maximum attainable specific growth rate during fed-batch cultivation. In this method, specific growth rate was changed from a maximum value of 0.55 h⁻¹ at the beginning of feeding and then it was reduced to 0.4 h⁻¹ at induction time.The final concentration of biomass and IFN-γ was reached to ∼115 g l⁻¹ (DCW) and 42.5 g(hIFN-γ) l⁻¹ after 16.5 h, also the final specific yield and overall productivity of recombinant hIFN-γ (rhIFN-γ) were obtained 0.37 g(hIFN-γ) g⁻¹ DCW and 2.57 g(hIFN-γ) l⁻¹ h⁻¹, respectively. According to available data this is the highest specific yield and productivity that has been reported for recombinant proteins production yet.