Predictive modeling and sensitivity analysis to estimate the experimental data of inulinase fermentation by Aspergillus niger grown on sugar beet molasses-based medium optimized using Plackett-Burman Design.

The present work aimed to model Aspergillus niger inulinase fermentation performed in the medium using sigmoidal functions, validate the selected models using an independent set of the experimental values, and perform a sensitivity analysis of the selected models. Based on the results, the selected models were Stannard and Fitzhugh models for substrate consumption (R2  = 0.9976 and 0.9974, respectively), Huang model for inulinase production (R2  = 0.9967), Weibull model for invertase-type production (R2  = 0.9963), and modified logistic model for invertase-type activity/inulinase activity ratio (R2  = 0.9292) with high R2 values (>0.90). Kinetics predicted by particularly selected models mentioned above fit well with the experimental kinetic results. Besides, validation of the selected models with an independent set of the experimental data indicated that they gave satisfying results with high R2 values for consumption and production (R2  > 0.90). Sensitivity analysis of the selected models showed that the yielded R2 values (R2  ≥ 0.9775) were in good agreement with those obtained from the selected models. Consequently, A. niger inulinase fermentation was successfully modeled and the selected models were successfully validated with an independent set of the observed data. Besides, the sensitivity analysis also verified the reliability of the selected models. Those models can serve as universal equations to describe the A. niger inulinase fermentation.

Optimization and kinetic modeling of media composition for hyaluronic acid production from carob extract with Streptococcus zooepidemicus.

Hyaluronic acid (HA), a mucopolysaccharide belonging to the glycosaminoglycan family, consists of repeating disaccharide units and has been used directly or indirectly in numerous human health practices. This study focused on evaluating carob pods for microbial HA production and kinetic modeling of HA fermentation. Therefore, the optimal medium composition was determined using Plackett-Burman Design (PBD) for HA production from carob extract with Streptococcus zooepidemicus. Maximum HA production of shake flask fermentation was 2.6 g/L (1.25 × 106) in the optimum medium, comprising 10°Bx of carob pods extract, 0.5 g/L of MgSO4.7H2O, 10.0 g/L of casein, 2.5 g/L of KH2PO4, 2.0 g/L of NaCl, 1.5 g/L of K2HPO4, 0.002 g/L of FeSO4 and 10.0 g/L of beef extract. In the continuation of the study, the fermentation performed with the optimal medium composition was modeled using three different models including the logistic model for biomass production, the Luedeking-Piret model for HA production, and the modified Luedeking-Piret model for substrate consumption. Based on the results, the experimental HA production data agreed with the Luedeking-Piret model with an R2 of 0.989. Since the α value was 63-fold higher than the value of ß, the HA production is growth-associated. Consequently, carob extract can be evaluated as a promising carbon source for producing HA.

Enhanced production of Aspergillus niger inulinase from sugar beet molasses and its kinetic modeling.

OBJECTIVE: The fermentation medium contains many complex components (vitamins, minerals, etc.) for better growth of the microorganisms. The increasing purity and number of these components used in the medium seriously affect the cost of the microbial process. This study aimed to further optimize the concentration of the components used in the medium (yeast extract and peptone) for inulinase fabrication by Aspergillus niger from sugar-beet molasses in shake flask fermentation by using Central Composite Design (CCD) and to kinetically identify the fermentation. RESULTS: The results indicated that the optimal medium composition consisted of only 4.2% (w/v) yeast extract. By using the fermentation environment, the inulinase generation, inulinase/sucrase ratio, maximum inulinase generation rate, maximum sugar depletion rate, and substrate utilization yield were determined as 1294.5 U/mL, 1.2, 159.6 U/mL/day, 7.4 g/L/day, and 98.1%, respectively. The kinetic analysis of the fungal development (logistic model) indicated that a specific development rate and initial biomass concentration were 0.89/day and 1.79 g/L, respectively. Inulinase and sucrase productions are mixed-development associated since the α value ≠ 0 (8.46 and 4.31 U/mgX) and the ß value ≠ 0 (5.15 and 4.83 U/mgX day), respectively (Luedeking-Piret model). Besides, the maintenance value (Z) (0.009 gS/gX day) was lower than γ value (1.044 gS/gX), showing that A. niger commonly uses the substrates for enzyme fabrication and fungal development (modified Luedeking-Piret model). CONCLUSIONS: The enzyme activity was increased by optimizing the concentration of the components used. It was demonstrated that the proposed kinetic models can victoriously define fungal development, enzyme fabrication, and sugar depletion.

Medium optimization and kinetic modeling for the production of Aspergillus niger inulinase.

The goals of this study were to optimize the medium formulation for enhanced production of Aspergillus niger inulinase using Plackett-Burman Design (PBD) and to model the fermentation in optimal medium formulation. Results indicated that (NH4)2SO4 (negative effect), yeast extract and peptone (positive effect) were determined as significant factors affecting the inulinase production. Different media including Medium A (non-enriched), Medium B (contains both negative and positive factors) and Medium C (contains only positive factors) were formed and inulinase fermentations were performed. Findings showed that the best nutritional formulation was Medium C, which yielded to be 1011.02 U/mL, 834.28 U/mL, 1.22, 4383.44 U/mg, 4186 U/mg, 158.49 U/mL/day, 128.60 U/mL/day and 94.54% of PInulinase, SInulinase, I/S ratio, SInulinase, SSucrase, QInulinase, QSucrase and SUY, respectively. Additionally, fungal growth, enzyme or protein production and substrate consumption were modeled using the logistic model, Luedeking-Piret model, and modified Luedeking-Piret model, respectively, and found that enzyme or protein production was non-growth associated. Besides, maintenance value (Z) was lower than γ value, indicating that A. niger mainly utilizes the sugars for enzyme production and fungal growth. Consequently, optimum medium composition was successfully determined by PBD and also the kinetic models fitted the experimental data very well with high regression coefficient.

A current approach to the control of filamentous fungal growth in media: microparticle enhanced cultivation technique.

Various strategies have been carried out to date in order to overcome the problem of the adverse effects of bulk fungal growth in bioreactors. Nevertheless, previous conventional methods such as modifying the cultivation temperature or pH resulted in limited biomass production and consequently lower yields. In recent years microparticle enhanced cultivation (MPEC) techniques are one of the most remarkable and novel methods employed for submerged fungal production to overcome bulk microbial growth. In addition to low cost advantages, MPEC also provides benefits such as not interfering with fungal metabolism, enhancing final product concentration and improving homogeneity in the fermentation broth. In this review, a comparison of conventional and novel methods to control fungal morphology has been discussed. Additionally, the application of microparticles in fungal fermentations, their benefits to the process in terms of fungal morphology, biomass accumulation, substrate consumption, and product formation also effect mechanisms of microparticle function are discussed in detail.

Evaluation of carbon sources for the production of inulinase by Aspergillus niger A42 and its characterization.

Inulinases are used for the production of high-fructose syrup and fructooligosaccharides, and are widely utilized in food and pharmaceutical industries. In this study, different carbon sources were screened for inulinase production by Aspergillus niger in shake flask fermentation. Optimum working conditions of the enzyme were determined. Additionally, some properties of produced enzyme were determined [activation (Ea)/inactivation (Eia) energies, Q10 value, inactivation rate constant (kd), half-life (t1/2), D value, Z value, enthalpy (ΔH), free energy (ΔG), and entropy (ΔS)]. Results showed that sugar beet molasses (SBM) was the best in the production of inulinase, which gave 383.73 U/mL activity at 30 °C, 200 rpm and initial pH 5.0 for 10 days with 2% (v/v) of the prepared spore solution. Optimum working conditions were 4.8 pH, 60 °C, and 10 min, which yielded 604.23 U/mL, 1.09 inulinase/sucrase ratio, and 2924.39 U/mg. Additionally, Ea and Eia of inulinase reaction were 37.30 and 112.86 kJ/mol, respectively. Beyond 60 °C, Q10 values of inulinase dropped below one. At 70 and 80 °C, t1/2 of inulinase was 33.6 and 7.2 min; therefore, inulinase is unstable at high temperatures, respectively. Additionally, t1/2, D, ΔH, ΔG values of inulinase decreased with the increase in temperature. Z values of inulinase were 7.21 °C. Negative values of ΔS showed that enzymes underwent a significant process of aggregation during denaturation. Consequently, SBM is a promising carbon source for inulinase production by A. niger. Also, this is the first report on the determination of some properties of A. niger A42 (ATCC 204,447) inulinase.

Controlling filamentous fungi morphology with microparticles to enhanced ß-mannanase production.

ß-mannanase was produced mainly by Aspergillus species and can degrade the ß-1,4-mannose linkages of galactomannans. This study was undertaken to enhance mannanase production using talcum and aluminum oxide as the microparticles, which control cell morphology of recombinant Aspergillus sojae in glucose and carob extract medium. Both microparticles improved fungal growth in glucose and carob pod extract medium. Aluminum oxide (1 g/L) was the best agent for glucose medium which resulted in 514.0 U/ml. However, the highest mannanase activity was found as 568.7 U/ml with 5 g/L of talcum in carob extract medium. Increase in microparticle concentration resulted in decreasing the pellet size diameter. Furthermore, more than 10 g/L of talcum addition changed the filamentous fungi growth type from pellet to pellet/mycelium mixture. Results showed that right type and concentration of microparticle in fermentation media improved the mannanase activity and production rate by controlling the growth morphology.

Microparticle-enhanced Aspergillus ficuum phytase production and evaluation of fungal morphology in submerged fermentation.

Phytase can be used in animal's diets to increase the absorption of several divalent ions, amino acids and proteins and to decrease the excessive phosphorus release in manure to prevent negative effects on the environment. This study aimed to enhance the current submerged fungal phytase productions with a novel fermentation technique by evaluating the effect of the various microparticles on Aspergillus ficuum phytase production. It was observed that microparticles prevented bulk fungal pellet growth, decreased average fungal pellet size and significantly increased phytase activity in the submerged fermentation. Microbial structure imaging results showed that the average fungal pellet radius decreased from 800 to 500 and 200 µm by addition of 15 g/L aluminum oxide and talcum, respectively, in shake-flask fermentation. Also, addition of 15 g/L of talcum and aluminum oxide increased phytase activity to 2.01 and 2.93 U/ml, respectively, compared to control (1.02 U/ml) in shake-flask fermentation. Additionally, phytase activity reached 6.49 U/ml within 96 h of fermentation with the addition of 15 g/L of talcum, whereas the maximum phytase activity was only 3.45 U/ml at 120 h of fermentation for the control in the 1-L working volume bioreactors. In conclusion, microparticles significantly increased fungal phytase activity and production yield compared to control fermentation.

Enhanced Aspergillus ficuum phytase production in fed-batch and continuous fermentations in the presence of talcum microparticles.

This study aimed to enhance Aspergillus ficuum phytase production in fed-batch and continuous fermentations with addition of talcum microparticles. Phytase activity almost doubled in fed-batch and continuous fermentations by addition of 15 g/l of talcum compared to the control. Effect of talcum on fungal morphology was also shown that addition of talcum provided smaller fungal pellets and more homogenized fermentation broth compared to the control. Average fungal pellet radius decreased from 500 to 100 µm by addition of 15 g/l of talcum in the bioreactors. Also, 15 g/l talcum addition increased phytase productivity and optimum dilution rate in the continuous fermentations from 0.293 to 0.621 U/ml/h and from 0.09 to 0.1/h, respectively, compared to control.

Production of ß-mannanase, inulinase, and oligosaccharides from coffee wastes and extracts.

This study aimed to produce enzymes (beta (ß)-mannanase using a recombinant Aspergillus sojae AsT3 and inulinase using Aspergillus niger A42) and oligosaccharides (mannooligosaccharides (MOS), fructooligosaccharides (FOS)) using coffee waste, ground coffee, and coffee extract by solid-state fermentation (SSF). Plackett-Burman Design (PBD) was used to create a design for enzyme production with four different parameters (temperature, pH, solid-to-liquid ratio (SLR), and mix with coffee wastes and ground coffee). The highest ß-mannanase and inulinase activities were 71.17 and 564.07 U/mg of protein respectively. Statistical analysis showed that the temperature was statistically significant for the production of both enzymes (P < 0.05). The produced enzymes were utilized in French Pressed coffee extracts to produce oligosaccharides. As a result of the enzymatic hydrolyzation, the highest mannobiose, mannotriose, mannotetraose, and total MOS levels were 109.66, 101.11, 391.02, and 600.64 ppm, respectively. For the FOS production, the maximal 1,1,1-kestopentaose was 38.34 ppm. Consequently, this study demonstrates that a recombinant Aspergillus sojae AsT3 ß-mannanase and Aspergillus niger A42 inulinase produced from coffee wastes and ground coffee can be used in coffee extracts to increase the amount of oligosaccharides in coffee extracts.

Inulinase and fructooligosaccharide production from carob using Aspergillus niger A42 (ATCC 204447) under solid-state fermentation conditions.

This study aimed to the production of inulinase and fructooligosaccharides (FOSs) from carob under the solid-state fermentation (SSF) conditions by using Plackett-Burman Design (PBD). Based on the results the maximum inulinase and specific inulinase activities were 249.98 U/mL and 318.29 U/mg protein, respectively. When the fructooligosaccharide (FOS) results were evaluated, the maximum values of 1,1,1-Kestopentaose, 1,1-Kestotetraose, and 1-Kestose were 182.01, 506.16, 132.16 ppm while the lowest and highest total FOS values were 179.35 and 516.66 ppm, respectively. On the other hand, it was observed that the maximum inulinase activity was found at the center points of the design. Therefore, validation fermentations were carried out at center point conditions. Subsequently, the yielded bulk enzyme extracts were partially purified using Spin-X UF membranes with 10, 30, and 50 kDa cut-off values. After purification, the maximum inulinase activity was 247.30 U/mg using a 50 kDa cut-off value. Followed by this process, the purified enzyme was used to produce FOSs and the results indicated that the maximum total FOS amount was 28,712.70 ppm. Consequently, this study successfully demonstrates that Aspergillus niger A42 inulinase produced from carob under the SSF conditions can be used in FOSs production.

Fermentable sugars production from wheat bran and rye bran: response surface model optimization of dilute sulfuric acid hydrolysis.

ABSTRACTOptimization of hydrolysis conditions of lignocellulosic biomass is crucial to able to produce value-added products by fermentation. This study not only determines optimal dilute sulfuric acid (H2SO4) hydrolysis conditions of wheat bran (WB) and rye bran (RB) by using one-factor-at-a-time method and subsequently Box-Behnken design but also elucidates chemical composition of hydrolysates yielded under optimal hydrolysis conditions. Based on the results, optimal hydrolysis conditions of WB and RB were 121 and 130°C of temperature, 1/8 and 1/8 w/v of solid to liquid ratio, 2.66 and 1.58% v/v of dilute H2SO4 ratio, and 30 and 16 min of implementation time, respectively. Hydrolysates obtained from WB and RB at these conditions contained 72.7 (0.58 g sugar/g biomass) and 89.4 g/L (0.72 g sugar/g biomass) of reducing sugar concentration, respectively. Hydrolysis rates of WB and RB were 87.79 and 91.33%, respectively. Main reducing sugar in RB hydrolysate was glucose with 31.17 g/L (0.25 g glucose/g biomass) while glucose and xylose were the main monosaccharides with 20.90 (0.17 g glucose/g biomass) and 18.69 g/L (0.15 g xylose/g biomass) in WB hydrolysate, respectively. With acidic hydrolysis of WB and RB, inhibitors such as phenolics, 5-Hydroxymethylfurfural, 2-Furaldehyde (not for RB), acetic acid, and formic acid (not for WB) formed. Catalytic efficiency values of H2SO4 for WB and RB were 15.2 and 24.4 g /g, respectively, indicating that inhibitor concentration in WB hydrolysate was higher than that of RB. These results indicated that WB and RB have a high potential in production of value-added products by fermentation.

Determination of D-pinitol in carob syrup.

Carob syrup is a traditional product native to the Mediterranean region, containing a high concentration of sugar, phenolic compounds and minerals. d-pinitol is a bioactive component extracted from legumes and has some beneficial effects on human metabolism. In this research, the d-pinitol content and sugar profile of 10 different carob syrup samples purchased from Turkish markets were determined. Mean d-pinitol, sucrose, glucose and fructose contents of samples were found to be 84.63 ± 10.73, 385.90 ± 45.07, 152.44 ± 21.72 and 162.03 ± 21.45 g/kg dry weight, respectively. Carob syrup has a considerable amount of d-pinitol compared with the other d-pinitol-including legumes. Consequently, this study showed that carob syrup may be a suitable source of d-pinitol for medical use and d-pinitol may be an indicator for the detection of any adulteration in carob syrup.

Partial purification and characterization of Aspergillus niger inulinase produced from sugar-beet molasses in the shaking incubator and stirred-tank bioreactors.

The objectives of this study were to purify Aspergillus niger inulinase produced from sugar-beet molasses in the shaking incubator (100 mL) and stirred-tank bioreactors (5-L and 30-L) by using some downstream processes and to determine enzyme kinetics and characterization. The results showed that the best centrifuge-time combination was 16,873 ×g-5 min with the purification coefficient of 1.4. Besides, with the ultrafiltration process, the inulinase activities yielded using the shaking incubator, pH-controlled/uncontrolled small-scale bioreactors, and large-scale bioreactor were increased from 1101.3, 2079.2, 1561.3, and 787.5 U/mL to 12,065.2, 21,789.0, 11,296.9, and 2948.1 U/mL with purification coefficients of 5.33, 1.38, 1.46, and 1.67, respectively. Additionally, for the inulinase from shaking incubator and pH-uncontrolled bioreactor, the values of Km for inulin and sucrose were 17.8 and 49.4 mg/mL and 28.8 and 25.9 mg/mL, respectively. As the enzyme amount added to the substrate increased, the activity also increased. Mn2+ is the activator of the enzyme, and Cu2+ and Ag+ are inhibitors of the enzyme. The molecular weight of inulinase has been determined to be between 60 and 70 kDa. Consequently, this study ensures valuable and significant information about the purification and characterization of inulinase for industrial implementations.

Inulinase production and mathematical modeling from carob extract by using Aspergillus niger.

The main objectives of the study were to produce inulinase from carob extract by Aspergillus niger A42 (ATCC 204447) and to model the inulinase fermentation in the optimum carob extract-based medium. In the study, carob extract was used as a novel and renewable carbon source in the production of A. niger inulinase. For medium optimization, eight different variables including initial sugar concentration (°Bx), (NH4 )2 HPO4 , MgSO4 .7H2 O, KH2 PO4 , NH4 NO3 , yeast extract, peptone, and ZnSO4 .7H2 O were employed. After fermentations, optimum medium composition contained 1% yeast extract in 5°Bx carob extract. As a result of the fermentation, the maximum inulinase activity, maximum invertase-type activity, I/S ratio, maximum inulinase- and invertase-type activity rates, maximum sugar consumption rate, and sugar utilization yield were 1507.03 U/ml, 1552.86 U/ml, 0.97, 175.82 and 323.76 U/ml/day, 13.26 g/L/day, and 98.52%, respectively. Regarding mathematical modeling, the actual inulinase production and sugar consumption data were successfully predicted by Baranyi and Cone models based on the model evaluation and validation results and the predicted kinetic values, respectively. Consequently, this was the first report in which carob extract was used in the production of inulinase as a carbon source. Additionally, the best-selected models can serve as universal equations in modeling the inulinase production and sugar consumption in shake flask fermentation with carob extract medium.

ß-Mannanase production and kinetic modeling from carob extract by using recombinant Aspergillus sojae.

The main objectives of this study were to optimize ß-mannanase fermentation conditions by using Response Surface Methodology (RSM) and to model kinetically using the kinetic models. Based on the results, the optimum fermentation conditions were found to be initial sugar concentration of 10°Bx, whey concentration of 0.75% [w/v], and inoculum size of 8% (v/v). Under optimized conditions, ß-mannanase activity (P), sugar consumed (ΔS), maximum ß-mannanase production rate (QP ), and sugar utilization yield (SUY) were 687.89 U/mL, 47.38 g/L, 118.54 U mL-1 day-1 , and 69.73%, respectively. Kinetic models were employed to describe the optimum ß-mannanase fermentation process. The kinetic analysis of ß-mannanase fermentation showed that ß-mannanase fermentation is growth associated because the α value (U/mgX) is approximately 330-fold higher than the ß value (U/mgX·hr). Nevertheless, maintenance value (Z) was lower than γ value, thus showing that Aspergillus niger mainly utilizes the sugars for ß-mannanase production and fungal growth. Consequently, carob extract and whey powder could be used to be cost-effective carbon and organic nitrogen sources, respectively. It was clearly indicated that the suggested kinetic models can successfully describe the fungal growth, ß-mannanase production, and substrate consumption.

Effect of different fermentation strategies on ß-mannanase production in fed-batch bioreactor system.

Mannanases, one of the important enzyme group for industry, are produced by numerous filamentous fungi, especially Aspergillus species with different fermentation methods. The aim of this study was to show the best fermentation method of ß-mannanase production for fungal growth in fermenter. Therefore, different fermentation strategies in fed-batch fermentation (suspended, immobilized cell, biofilm and microparticle-enhanced bioreactor) were applied for ß-mannanase production from glucose medium (GM) and carob extract medium (CEM) by using recombinant Aspergillus sojae. The highest ß-mannanase activities were obtained from microparticle-enhanced bioreactor strategy. It was found to be 347.47 U/mL by adding 10 g/L of Al2O3 to GM and 439.13 U/mL by adding 1 g/L of talcum into CEM. The maximum ß-mannanase activities for suspended, immobilization, and biofilm reactor remained at 72.55 U/mL in GM, 148.81 U/mL in CEM, and 194.09 U/mL in GM, respectively. The reason for that is the excessive, and irregular shaped growth and bulk formation, inadequate oxygen transfer or substrate diffusion in bioreactor. Consequently, the enzyme activity was significantly enhanced by addition of microparticles compared to other fed-batch fermentation strategies. Also, repeatable ß-mannanase activities were obtained by controlling of the cell morphology by adding microparticle inside the fermenter.

Microparticle-enhanced polygalacturonase production by wild type Aspergillus sojae.

Polygalacturonases (PGs), an important industrial enzyme group classified under depolymerases, catalyze the hydrolytic cleavage of the polygalacturonic acid chain through the introduction of water across the oxygen bridge. In order to produce and increase the concentration of this enzyme group in fermentation processes, a new approach called microparticle cultivation, a promising and remarkable method, has been used. The aim of this study was to increase the PG activity of Aspergillus sojae using aluminum oxide (Al2O3) as microparticles in shake flask fermentation medium. Results indicated that the highest PG activity of 34.55 ± 0.5 U/ml was achieved with the addition of 20 g/L of Al2O3 while the lowest activity of 15.20 ± 0.2 U/mL was obtained in the presence of 0.1 g/L of Al2O3. In fermentation without microparticles as control, the activity was 15.64 ± 3.3 U/mL. Results showed that the maximum PG activity was 2.2-fold higher than control. Additionally, smaller pellets formed with the addition of Al2O3 where the lowest pellet diameter was 955.1 µm when 10 g/L of the microparticle was used. Also, it was noticed that biomass concentration gradually increased with increasing microparticle concentration in the fermentation media. Consequently, the PG activity was significantly increased in microparticle-enhanced shake flask fermentation. In fact, these promising preliminary data can be of significance to improve the enzyme activity in large-scale bioreactors.

Ethanol production from rice hull using Pichia stipitis and optimization of acid pretreatment and detoxification processes.

The goal of this study was to produce ethanol from rice hull hydrolysates (RHHs) using Pichia stipitis strains and to optimize dilute acid hydrolysis and detoxification processes by response surface methodology (RSM). The optimized conditions were found as 127.14°C, solid:liquid ratio of 1:10.44 (w/v), acid ratio of 2.52% (w/v), and hydrolysis time of 22.01 min. At these conditions, the fermentable sugar concentration was 21.87 g/L. Additionally, the nondetoxified RHH at optimized conditions contained 865.2 mg/L phenolics, 24.06 g/L fermentable sugar, no hydroxymethylfurfural (HMF), 1.62 g/L acetate, 0.36 g/L lactate, 1.89 g/L glucose, and 13.49 g/L fructose + xylose. Furthermore, RHH was detoxified with various methods and the best procedures were found to be neutralization with CaO or charcoal treatment in terms of the reduction of inhibitory compounds as compared to nondetoxified RHH. After detoxification procedures, the content of hydrolysates consisted of 557.2 and 203.1 mg/L phenolics, 19.7 and 21.60 g/L fermentable sugar, no HMF, 0.98 and 1.39 g/L acetate, 0 and 0.04 g/L lactate, 1.13 and 1.03 g/L glucose, and 8.46 and 12.09 g/L fructose + xylose, respectively. Moreover, the base-line mediums (control), and nondetoxified and detoxified hydrolysates were used to produce ethanol by using P. stipitis strains. The highest yields except that of base-line mediums were achieved using neutralization (35.69 and 38.33% by P. stipitis ATCC 58784 and ATCC 58785, respectively) and charcoal (37.55% by P. stipitis ATCC 58785) detoxification methods. Results showed that the rice hull can be utilized as a good feedstock for ethanol production using P. stipitis. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:872-882, 2016.

Ultrasound-assisted dilute acid hydrolysis of tea processing waste for production of fermentable sugar.

Lignocellulosic materials that are the most abundant plant biomass in the world have the potential to become sustainable sources of the produced value added products. Tea processing waste (TPW) is a good lignocellulosic source to produce the value added products from fermentable sugars (FSs). Therefore, the present study is undertaken to produce FSs by using ultrasound-assisted dilute acid (UADA) and dilute acid (DA) hydrolysis of TPW followed by enzymatic hydrolysis. UADA hydrolysis of TPW was optimized by response surface methodology (RSM) at maximum power (900 W) for 2 h. The optimum conditions were determined as 50°C, 1:6 (w/v) solid:liquid ratio, and 1% (w/v) DA concentration, which yielded 20.34 g/L FS concentration. Furthermore, its DA hydrolysis was also optimized by using RSM for comparison and the optimized conditions were found as 120°C, 1:8 solid:liquid ratio, and 1% acid concentration, which produced 25.3 g/L FS yield. Even though the produced sugars with UADA hydrolysis are slightly less, but it can provide significant cost saving due to the lower temperature requirement and less liquid consumption. Besides, enzymatic hydrolysis applied after pretreatments of TPW were very more economic than the conventional enzymatic hydrolysis in the literature due to shorter time requiring. In conclusion, ultrasound-assisted is a promising technology that can be successfully applied for hydrolysis of biomass and can be an alternative to the other hydrolysis procedures and also TPW can be considered as suitable carbon source for the production of value-added products like biofuels, organic acids, and polysaccharides. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:393-403, 2016.