Efficient bioconversion from acid hydrolysate of waste oleaginous yeast biomass after microbial oil extraction to bacterial cellulose by Komagataeibacter xylinus

Biomass acid hydrolysate of oleaginous yeast Trichosporon cutaneum after microbial oil extraction was applied as substrate for bacterial cellulose (BC) production by Komagataeibacter xylinus (also named as Gluconacetobacter xylinus previously) for the first time. BC was synthesized in static culture for 10 days, and the maximum BC yield (2.9?g/L) was got at the 4th day of fermentation. Most carbon sources in the substrate (glucose, mannose, formic acid, acetic acid) can be utilized by K. xylinus. The highest chemical oxygen demand (COD) removal (40.7?±?3.0%) was obtained at the 6th day of fermentation, and then the COD increased possibly due to the degradation of BC. The highest BC yield on COD consumption was 38.7?±?4.0% (w/w), suggesting that this is one efficient bioconversion for BC production. The BC structure was affected little by the substrate by comparison with that generated in classical HS medium using field-emission scanning electron microscope (FE-SEM), Fourier transform infrared, and X-ray diffraction. Overall, this technology can both solve the issue of waste oleaginous yeast biomass and produce valuable biopolymer (BC).     

Biotransformation of furfural by yeast cells covalently bound to cellulose granules

A covalent binding to cellulose granules of two yeast strains Candida tropicalis and Trichosporon cutaneum was achieved. The maximum activity for destroying furfural by the immobilized cells was obtained when the procedure conditions were: reaction medium at pH 5.0, 20°C and cell suspension concentration of 80 mg/ml. The continuous furfural transformation was studied using a growth medium in a fermenter with immobilized Trichosporon cutaneum in which a 84% bioconversion was achieved. The reduced values of furfural remained constant even after 10-fold transformation.     

Production of cellulases by Thermomucor indicae-seudaticae: characterization of a thermophilic β-glucosidase

Abstract

The current study evaluated the production and characterization of β-glucosidase by the thermophilic fungus Thermomucor indicae-seudaticae in solid-state fermentation of wheat bran. Isolated fungi have significant amounts of β-glucosidase, an enzyme that may be applied to different industrial processes, such as the production of fuels, food, and other chemical compounds. Maximal enzyme activity occurred in pH 3.5–4.5 and at 70?°C. The enzyme exhibited high thermostability, for 1?h, up to 60?°C, and good tolerance to glucose (10?mM) and ethanol (10%). The optimization of fermentative parameters on the production of β-glucosidase was carried out by evaluating the best supplementary nutrient source, pH of nutrient solution, initial substrate moisture and fermentation temperature. The optimization of the above fermentation parameters increased enzyme activity by 120.0%. The highest enzymatic activity (164.0?U/g) occurred with wheat bran containing 70% initial moisture, supplemented with 1.0% (NH₄)₂SO₄ solution at pH 5.5–6.0 and fungus incubated at 40?°C. A more detailed study of β-glucosidase suggested that Sulfur is an important component of the main amino acid present in this enzyme. The enhancer of the enzyme activity occurred when the fungus was grown on wheat bran supplemented with a sulfur-containing solution. In fact, increasing the concentration of sulfur in the solution increased its activity.     

Use of elephant grass (Pennisetum purpureum) acid hydrolysate for microbial oil production by Trichosporon cutaneum

Elephant grass (Pennisetum purpureum) dilute acid hydrolysate contains 34.6?g/L total sugars. The potential of lipid production by oleaginous yeast Trichosporon cutaneum grown on elephant grass acid hydrolysate was investigated for the first time. During the fermentation process on the elephant grass acid hydrolysate, glucose, xylose, and arabinose could be well utilized as carbon sources by T. cutaneum. Interestingly, xylose was almost no use before glucose was consumed completely. This illustrated that simultaneous saccharification of xylose and glucose by T. cutaneum did not occur on elephant grass acid hydrolysate. The highest biomass, lipid content, lipid yield, and lipid coefficient of T. cutaneum were measured after the sixth day of fermentation and were 22.76?g/L, 24.0%, 5.46?g/L, and 16.1%, respectively. Therefore, elephant grass is a promising raw material for microbial oil production by T. cutaneum.     

Optimization of bioconversion conditions for vitamin D3 to 25-hydroxyvitamin D using Pseudonocardia autotrophica CGMCC5098

The optimal culture conditions for bioconversion of vitamin D₃ to calcifediol (25(OH)D₃) were investigated by varying carbon and nitrogen sources, metal salt concentrations, initial pH, temperature, solvents, surfactants, and agitation speed. In the process of this microbial hydroxylation, the timing of the addition of vitamin D₃, which is dissolved in ethanol, is of critical importance. Besides, the concentration of ethanol in zymotic fluid is the key factor to get high conversion ratio of vitamin D₃. In particular, the optimal culture conditions were 1.5% glucose, 1.5% soybean cake meal, 0.5% yeast extract, 0.5% corn steep liquor, 0.3% CaCO₃, 0.1% NaCl, 0.2% KH₂PO₄, pH 7.2 at 27?°C and the timing of the addition of vitamin D₃ dissolved in 5% (v/v) ethanol was 48?h followed by the inoculation of seed culture broth. Under the optimized conditions, the conversion of vitamin D₃ (1?g/L) by Pseudonocardia autotrophica CGMCC5098 in 50?L fermenter resulted in about 61.31% bioconversion ratio (639?mg/L) of 25(OH)D₃ on the 5th day.     

Butanol production from sweet sorghum bagasse with high solids content: Part I—comparison of liquid hot water pretreatment with dilute sulfuric acid

In these studies, we pretreated sweet sorghum bagasse (SSB) using liquid hot water (LHW) or dilute H₂SO₄ (2 g L^?1) at 190°C for zero min (as soon as temperature reached 190°C, cooling was started) to reduce generation of sugar degradation fermentation inhibiting products such as furfural and hydroxymethyl furfural (HMF). The solids loading were 250–300 g L^?1. This was followed by enzymatic hydrolysis. After hydrolysis, 89.0 g L^?1 sugars, 7.60 g L^?1 acetic acid, 0.33 g L^?1 furfural, and 0.07 g L^?1 HMF were released. This pretreatment and hydrolysis resulted in the release of 57.9% sugars. This was followed by second hydrolysis of the fibrous biomass which resulted in the release of 43.64 g L^?1 additional sugars, 2.40 g L^?1 acetic acid, zero g L^?1 furfural, and zero g L^?1 HMF. In both the hydrolyzates, 86.3% sugars present in SSB were released. Fermentation of the hydrolyzate I resulted in poor acetone‐butanol‐ethanol (ABE) fermentation. However, fermentation of the hydrolyzate II was successful and produced 13.43 g L^?1 ABE of which butanol was the main product. Use of 2 g L^?1 H₂SO₄ as a pretreatment medium followed by enzymatic hydrolysis resulted in the release of 100.6–93.8% (w/w) sugars from 250 to 300 g L^?1 SSB, respectively. LHW or dilute H₂SO₄ were used to economize production of cellulosic sugars from SSB. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:960–966, 2018     

Characterization of a recombinant cold-adapted purine nucleoside phosphorylase and its application in ribavirin bioconversion

Ribavirin is a broad-spectrum antiviral drug and can be produced by enzymatic synthesis by purine nucleoside phosphorylase (PNP). In this study, we describe the application of such a cold-adapted XmPNP in ribavirin bioconversion which showed approximately 15°C lower optimum temperature and 1.80-fold higher catalytic efficiency (k_cat/K_m) at 37°C within substrate inosine than homolog in E. coli. By contrast, E. coli (XmPNP) took only 12 h to reach maximum substrate conversion rate (70%) under its optimum temperature (50°C) by using recombinant strain cell as enzyme source, but E. coli (EcPNP) did at 24 h. These results suggest cold-adapted PNP is one attractive candidate for ribavirin bioconversion and other nucleoside medications to improve the catalytic efficiency.     

Production of L-malate from fumarate by the yeast Dipodascus magnusii

An alternative microbiological method for the production of malate from fumarate is presented. The yeast Dipodascus magnusii was used for this bioconversion. The optimum cell growth temperature was 28°C and the working volume 120 ml. The highest level of fumarase activity during bioconversion was achieved at a pH of 7.5 and a temperature of 37°C. These conditions were determined as optimal. Using sodium fumarate (1M), the maximum specific productivity of malic acid obtained was 1.72 g/(g_DCW × h) for intact cells. In the case of ammonium fumarate, it was 2.25 g/(g_DCW × h).     

High-titer n-butanol production by clostridium acetobutylicum JB200 in fed-batch fermentation with intermittent gas stripping

Acetone–butanol–ethanol (ABE) fermentation with a hyper‐butanol producing Clostridium acetobutylicum JB200 was studied for its potential to produce a high titer of butanol that can be readily recovered with gas stripping. In batch fermentation without gas stripping, a final butanol concentration of 19.1 g/L was produced from 86.4 g/L glucose consumed in 78 h, and butanol productivity and yield were 0.24 g/L h and 0.21 g/g, respectively. In contrast, when gas stripping was applied intermittently in fed‐batch fermentation, 172 g/L ABE (113.3 g/L butanol, 49.2 g/L acetone, 9.7 g/L ethanol) were produced from 474.9 g/L glucose in six feeding cycles over 326 h. The overall productivity and yield were 0.53 g/L h and 0.36 g/g for ABE and 0.35 g/L h and 0.24 g/g for butanol, respectively. The higher productivity was attributed to the reduced butanol concentration in the fermentation broth by gas stripping that alleviated butanol inhibition, whereas the increased butanol yield could be attributed to the reduced acids accumulation as most acids produced in acidogenesis were reassimilated by cells for ABE production. The intermittent gas stripping produced a highly concentrated condensate containing 195.9 g/L ABE or 150.5 g/L butanol that far exceeded butanol solubility in water. After liquid–liquid demixing or phase separation, a final product containing ～610 g/L butanol, ～40 g/L acetone, ～10 g/L ethanol, and no acids was obtained. Compared to conventional ABE fermentation, the fed‐batch fermentation with intermittent gas stripping has the potential to reduce at least 90% of energy consumption and water usage in n‐butanol production from glucose. Biotechnol. Bioeng. 2012; 109: 2746–2756. © 2012 Wiley Periodicals, Inc.     

OPTIMIZATION OF FERMENTATION CONDITIONS AND PURIFICATION OF CORDYCEPIN FROM Cordyceps militaris

The fermentation medium and conditions for the production of cordycepin were optimized in static culture using single-factor experiments, Placket–Burman design, a central composite design, and response surface methodology. Among seven variables including temperature, pH, and the concentrations of glucose, tryptone, yeast extract, KH₂PO₄, and MgSO₄ · 7H₂O, temperature and the concentrations of yeast extract and tryptone were found to be the important factors that significantly affected cordycepin production. The optimized medium consisted of yeast extract 9.00 g/L and tryptone 17.10 g/L, while the optimized culture conditions consisted of seed age 3 days, with an inoculum size of 10% and incubation temperature of 27.1°C. A maximum cordycepin yield of 7.35 g/L was achieved in a 5-L fermenter under the optimized conditions. Next, cordycepin was partially purified and determined. The resulting product showed 90.54% high-performance liquid chromatography (HPLC)–ultraviolet (UV) purity. Therefore, cordycepin was applied to a cell viability assay on SH-SY5Y cells and RM-1 cells. Cordycepin can inhibit the proliferation of RM-1 cells with IC₅₀ of 133 µmol/L, but it has no inhibitory effect on SH-SY5Y cells.

Supplemental materials are available for this article. Go to the publisher's online edition of Preparative Biochemistry and Biotechnology to view the supplemental file.     

Cellulosic Butanol (ABE) Biofuel Production from Sweet Sorghum Bagasse (SSB): Impact of Hot Water Pretreatment and Solid Loadings on Fermentation Employing <Emphasis Type="Italic">Clostridium beijerinckii</Emphasis> P260

A novel butanol fermentation process was developed in which sweet sorghum bagasse (SSB) was pretreated using liquid hot water (LHW) pretreatment technique followed by enzymatic hydrolysis and butanol (acetone butanol ethanol (ABE)) fermentation. A pretreatment temperature of 200 °C resulted in the generation of a hydrolyzate that inhibited butanol fermentation. When SSB pretreatment temperature was decreased to 190 °C (0-min holding time), the hydrolyzate was successfully fermented without inhibition and an ABE productivity of 0.51 g L^?1 h^?1 was achieved which is comparable to the 0.49 g L^?1 h^?1 observed in the control fermentation where glucose was used as a feedstock. These results are based on the use of 86 g L^?1 SSB solid loadings in the pretreatment reactors. We were also able to increase SSB solid loadings from 120 to 200 g L^?1 in the pretreatment step (190 °C) followed by hydrolysis and butanol fermentation. As pretreatment solid loadings increased, ABE yield remained in the range of 0.38–0.46. In these studies, a maximum ABE concentration of 16.88 g L^?1 was achieved. Using the LHW pretreatment technique, 88.40–96.00 % of polymeric sugars (cellulose + hemicellulose) were released in the SSB hydrolyzate. The LHW pretreatment technique does not require chemical additions and is environmentally friendly, and the hydrolyzate can be used successfully for butanol fermentation.     

Biochemical and biotechnological studies on a novel purified bacillus cholesterol oxidase tolerant to solvent and thermal stress

A novel bacterial strain was isolated and identified as Bacillus pumilus, with the capability to produce cholesterol oxidase enzyme (55?kDa). The production of the enzyme was optimized via two-step statistical approach. Out of eight factors screened in Plackett–Burman, only four had significant effects on enzyme activity. The optimization process of these four variables by Box–Behnken revealed that the maximum enzyme activity (90?U/mL) was significantly obtained after 6 days of fermentation with 0.3%, 1% and 0.2% of NH₄NO₃, yeast extract and Tween 80, respectively. The purified enzyme showed optimum activity at pH 7.5 and temperature of 40?°C. The enzyme retained 100% of its activity after storage at 40?°C for 60?min. The enzyme also exhibited enhanced stability in the presence of Tween 80, methanol and isopropanol. This solvent and thermal stress tolerant enzyme, produced by B. pumilus, may provide a practical option for industrial and analytical applications.     

Effect of temperature on ethanol tolerance of thermotolerant Isshatchenkia orientalis IPE100

Tolerance to high temperature and ethanol is a major factor in high‐temperature bio‐ethanol fermentation. The inhibitory effect of exogenously added ethanol (0–100 g L^?1) on the growth of the newly isolated thermotolerant Issatchenkia orientalis IPE100 was evaluated at a range of temperatures (30–45°C). A generalized Monod equation with product inhibition was used to quantify ethanol tolerance, and it correlated well with the experimental data on microbial growth inhibition of ethanol at the temperatures of 30–45°C. The maximum inhibitory concentration of ethanol for growth (P_m) and toxic power (n) at the optimal growth temperature of 42°C were estimated to be 96.7 g L^?1 and 1.23, respectively. The recently isolated thermotolerant I. orientalis IPE100 shows therefore a strong potential for the development of future high‐temperature bio‐ethanol fermentation technologies. This study provides useful insights into our understanding of the temperature‐dependent inhibitory effects of ethanol on yeast growth.     

Optimization of Fermentation Medium and Conditions for Mycelial Growth and Water-soluble Exo-polysaccharides Production by Isaria farinosa B05

Abstract

The optimal fermentation medium and conditions for mycelial growth and water-soluble exo-polysaccharides production by Isaria farinosa B05 were investigated. The medium components and fermentation conditions were optimized according to the one at a time method, while the concentration of medium components was determined by the orthogonal matrix method. The results showed that the optimal fermentation medium was as follows: sucrose 3.5% (w/v), peptone 0.5%, yeast extract 0.2%, K₂HPO₄ 0.1%, and MgSO₄ 0.05%. The suitable fermentation conditions were as follows: initial pH 7.0, temperature 25°C, medium volume 75 mL/250 mL, inoculum volume 5% (v/v), time 5d. In such optimal nutrition and environmental conditions, the maximal mycelial yield was 2.124 g/100 mL after 4 day's fermentation, while maximal water-soluble exo-polysaccharides production reached 2.144 g/L after 5 day's fermentation.     

Optimisation of medium and culture conditions for the production of antifungal substances to Colletotrichum musae by Trametes elegans SR06

An endophytic fungus SR06 was isolated from a leaf of Amomum villosum Lour., which had a high antagonistic effect on Colletotrichum musae with an inhibition ratio of 41.20%. The antifungal substances could be secreted into fermentation broth, which had a high inhibitory activity. Strain SR06 was identified as Trametes elegans according to internal transcribed spacer sequence analysis. Response surface methodology (RSM) was used to optimise the process parameters of antifungal substances production. Using the Plackett–Burman design, three variables (glucose, yeast extract and MgSO₄·7H₂O) exerted significant effects on antifungal substances production. Then RSM experiments were conducted to further optimise the three variables. The optimal medium components were 26.45?g/L glucose, 10?g/L peptone, 14.96?g/L yeast extract and 1.49?g/L MgSO₄·7H₂O, and the optimal initial pH was 6.0, with a culture temperature of 28°C and a shaking speed of 180?rpm. Under the optimised conditions, a significant improvement in the production of antifungal substances by T. elegans SR06 was accomplished, and the inhibition zone diameter was up to 29.2?mm after culturing for 7d. The average control efficacy of the fermentation supernatant of SR06 against C. musae was 51.29% on banana fruits, which was significantly higher than that of the fungicide carbendazim.     

Recent advances on conversion and co-production of acetone-butanol-ethanol into high value-added bioproducts

Butanol is an important bulk chemical and has been regarded as an advanced biofuel. Large-scale production of butanol has been applied for more than 100 years, but its production through acetone–butanol–ethanol (ABE) fermentation process by solventogenic Clostridium species is still not economically viable due to the low butanol titer and yield caused by the toxicity of butanol and a by-product, such as acetone. Renewed interest in biobutanol as a biofuel has spurred technological advances to strain modification and fermentation process design. Especially, with the development of interdisciplinary processes, the sole product or even the mixture of ABE produced through ABE fermentation process can be further used as platform chemicals for high value added product production through enzymatic or chemical catalysis. This review aims to comprehensively summarize the most recent advances on the conversion of acetone, butanol and ABE mixture into various products, such as isopropanol, butyl-butyrate and higher-molecular mass alkanes. Additionally, co-production of other value added products with ABE was also discussed.     

Yeast screening from avermectins wastewater and investigation on the ability of its fermentation

Wastewater from avermectin production is refractory with high output, high chemical oxygen demand (COD) concentration and high cost further. The current wastewater treatment technology, with little reuse of the organic material, needs high dilution ratio during treatment. Yeast single cell protein was produced from the wastewater of avermectins fermentation in this research. First, the yeast strain (H-1) which show enough tolerance to avermectins residue was screened from the wastewater, and it was identified as being most closely related to Candida tropicalis (100%, EF120592.1) using 18S rDNA gene sequence analysis. Second, its growth characteristics in the avermectins wastewater were studied. The dry biomass reached the maximal point of 10 g/L, the COD removal was up to 66.67%, and avermectins removal in the wastewater was 99.48% at the optimal condition that it was liquid volume 50 ml (250 ml flask), pH 4.0, temperature 30°C, inoculum volume 10% (V/V) and fermentation period 20 h. Third, the nutritional contents of dry yeast powder were determined, in which the water content was 8.12%, ash content was 5.18% and the crude protein was 40.02%. The dry yeast powder from avermectin waste liquor was promising to be used as a raw material or nitrogen source for commercial production of avermectins. The project was economically feasible by primary cost accounting.     

The fermentation stoichiometry of Thermotoga neapolitana and influence of temperature,oxygen, and pH on hydrogen production

The hyperthermophilic bacterium, Thermotoga neapolitana, has potential for use in biological hydrogen (H₂) production. The objectives of this study were to (1) determine the fermentation stoichiometry of Thermotoga neapolitana and examine H₂ production at various growth temperatures, (2) investigate the effect of oxygen (O₂) on H₂ production, and (3) determine the cause of glucose consumption inhibition. Batch fermentation experiments were conducted at temperatures of 60, 65, 70, 77, and 85°C to determine product yield coefficients and volumetric productivity rates. Yield coefficients did not show significant changes with respect to growth temperature and the rate of H₂ production reached maximum levels in both the 77°C and 85°C experiments. The fermentation stoichiometry for T. neapolitana at 85°C was 3.8 mol H₂, 2 mol CO₂, 1.8 mol acetate, and 0.1 mol lactate produced per mol of glucose consumed. Under microaerobic conditions H₂ production did not increase when compared to anaerobic conditions, which supports other evidence in the literature that T. neapolitana does not produce H₂ through microaerobic metabolism. Glucose consumption was inhibited by a decrease in pH. When pH was adjusted with buffer addition cultures completely consumed available glucose. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Growth of <Emphasis Type="Italic">Salinispora tropica</Emphasis> strains CNB440, CNB476, and NPS21184 in nonsaline,low-sodium media

Effective wastewater treatment using microbial fuel cells (MFCs) will require a better understanding of how operational parameters and solution chemistry affect treatment efficiency, but few studies have examined power generation using actual wastewaters. The efficiency of wastewater treatment of a beer brewery wastewater was examined here in terms of maximum power densities, Coulombic efficiencies (CEs), and chemical oxygen demand (COD) removal as a function of temperature and wastewater strength. Decreasing the temperature from 30°C to 20°C reduced the maximum power density from 205 mW/m² (5.1 W/m³, 0.76 A/m²; 30°C) to 170 mW/m² (20°C). COD removals (R _COD) and CEs decreased only slightly with temperature. The buffering capacity strongly affected reactor performance. The addition of a 50-mM phosphate buffer increased power output by 136% to 438 mW/m², and 200 mM buffer increased power by 158% to 528 mW/m². In the absence of salts (NaCl), maximum power output varied linearly with wastewater strength (84 to 2,240 mg COD/L) from 29 to 205 mW/m². When NaCl was added to increase conductivity, power output followed a Monod-like relationship with wastewater strength. The maximum power (P _max) increased in proportion to the solution conductivity, but the half-saturation constant was relatively unaffected and showed no correlation to solution conductivity. These results show that brewery wastewater can be effectively treated using MFCs, but that achievable power densities will depend on wastewater strength, solution conductivity, and buffering capacity.     

Coupling glucose fermentation and homoacetogenesis for elevated acetate production: Experimental and mathematical approaches

Homoacetogenesis is an important potential hydrogen sink in acetogenesis, in which hydrogen is used to reduce carbon dioxide to acetate. So far the acetate production from homoacetogenesis, especially its kinetics, has not been given sufficient attention. In this work, enhanced production of acetate from anaerobic conversion of glucose through coupling glucose fermentation and homoacetogenesis is investigated with both experimental and mathematical approaches. Experiments are conducted to explore elevated acetate production in a coupled anaerobic system. Acetate production could be achieved by homoacetogenesis with a relative high acetate yield under mixed fermentation conditions. With the experimental observations, a kinetic model is formulated to describe such a homoacetogenic process. The maximum homoacetogenic rate (k_m,homo) is estimated to be 28.5 ± 1.7 kg COD kg⁻¹ COD day⁻¹ with an uptake affinity constant of 3.7 × 10⁻⁵ ± 3.1 × 10⁻⁶ kg COD m⁻³. The improved calculation of homoacetogenic kinetics by our approach could correct the underestimation of homoacetogenesis in anaerobic fermentation processes, as it often occurs in these systems supported by literature analysis. The model predictions match the experimental results in different cases well and provide insights into the dynamics of anaerobic glucose conversion and acetate production. Furthermore, acetate production via homoacetogenesis increases by about 40% through utilizing the fed‐batch coupling system, attributed to a balance between the hydrogen production in the acetogenesis phase and the hydrogen consumption in the homoacetogenesis phase. This work provides an effective way for increased anaerobic acetate production, and gives us a better understanding about the homoacetogenic kinetics in the anaerobic fermentation process. Biotechnol. Bioeng. 2011;108: 345–353. © 2010 Wiley Periodicals, Inc.