Characterization and improvement of oxygen transfer in pilot plant external air-lift bioreactor for mycelial biomass production

The oxygen transfer dynamics in a pilot plant external air-lift bioreactor (EALB) during the cultivation of mycelial biomass were characterized with respect to hydrodynamic parameters of gas holdup (ε), oxygen transfer coefficient (KLa) and superficial gas velocity (U g), and dissolved oxygen (DO). An increased flow rate of air supply was required to meet the increased oxygen demand with mycelial biomass growth. Consequently, an increase in air flow rate led to an increase in ε, KLa and the DO level. The enhancement of oxygen transfer rate in the cultivated broth system, however, was limited with highly increased viscosity of the mycelial broth. An increase in air flow rate from 1.25 to 2.00 v/v/m resulted in a low increment of oxygen transfer. The newly designed pilot plant EALB with two air spargers significantly improved processing reliability, aeration rate and KLa. The pilot plant EALB process, operated under a top pressure from 0 to 1.0 bars, also demonstrated a significant improvement of oxygenation efficiency by more than 20% in DO and KLa. The performance of the two sparger EALB process under top pressure demonstrated an efficient and economical aerobic system with fast mycelial growth and high biomass productivity in mycelial biomass production and wastewater treatment

Evaluation of Potential Fungal Species for the in situ Simultaneous Saccharification and Fermentation (SSF) of Cellulosic Material

Three fungal species were evaluated for their abilities to saccharify pure cellulose. The three species chosen represented three major wood-rot molds; brown rot (Gloeophyllum trabeum), white rot (Phanerochaete chrysosporium) and soft rot (Trichoderma reesei). After solid state fermentation of the fungi on the filter paper for four days, the saccharified cellulose was then fermented to ethanol by using Saccharomyces cerevisiae. The efficiency of the fungal species in saccharifying the filter paper was compared against a low dose (25 FPU/g cellulose) of a commercial cellulase. Total sugar, cellobiose and glucose were monitored during the fermentation period, along with ethanol, acetic acid and lactic acid. Results indicated that the most efficient fungal species in saccharifying the filter paper was T. reesei with 5.13 g/100 g filter paper of ethanol being produced at days 5, followed by P. chrysosporium at 1.79 g/100 g filter paper. No ethanol was detected for the filter paper treated with G. trabeum throughout the five day fermentation stage. Acetic acid was only produced in the sample treated with T. reesei and the commercial enzyme, with concentration 0.95 and 2.57 g/100 g filter paper, respectively at day 5. Lactic acid production was not detected for all the fungal treated filter paper after day 5. Our study indicated that there is potential in utilizing in situ enzymatic saccharification of biomass by using T. reesei and P. chrysosporium that may lead to an economical simultaneous saccharification and fermentation process for the production of fuel ethanol

Solid-Substrate Fermentation of Corn Fiber by Phanerochaete chrysosporium and Subsequent Fermentation of Hydrolysate into Ethanol

The goal of this study was to develop a fungal process for ethanol production from corn fiber. Laboratory-scale solid-substrate fermentation was performed using the white-rot fungusPhanerochaete chrysosporium in 1 L polypropylene bottles as reactors via incubation at 37 °C for up to 3 days. Extracellular enzymes produced in situ by P. chrysosporium degraded lignin and enhanced saccharification of polysaccharides in corn fiber. The percentage biomass weight loss and Klason lignin reduction were 34 and 41%, respectively. Anaerobic incubation at 37 °C following 2 day incubation reduced the fungal sugar consumption and enhanced the in situ cellulolytic enzyme activities. Two days of aerobic solid-substrate fermentation of corn fiber with P. chrysosporium, followed by anaerobic static submerged-culture fermentation resulted in 1.7 g of ethanol/100 g of corn fiber in 6 days, whereas yeast (Saccharomyces cerevisiae) cocultured with P. chrysosporium demonstrated enhanced ethanol production of 3 g of ethanol/100 g of corn fiber. Specific enzyme activity assays suggested starch and hemi/cellulose contribution of fermentable sugar

Enzyme Production by Wood-Rot and Soft-Rot Fungi Cultivated on Corn Fiber Followed by Simultaneous Saccharification and Fermentation

This research aims at developing a biorefinery platform to convert lignocellulosic corn fiber into fermentable sugars at a moderate temperature (37 °C) with minimal use of chemicals. White-rot (Phanerochaete chrysosporium), brown-rot (Gloeophyllum trabeum), and soft-rot (Trichoderma reesei) fungi were used for in situ enzyme production to hydrolyze cellulosic and hemicellulosic components of corn fiber into fermentable sugars. Solid-substrate fermentation of corn fiber by either white- or brown-rot fungi followed by simultaneous saccharification and fermentation (SSF) with coculture of Saccharomyces cerevisiae has shown a possibility of enhancing wood rot saccharification of corn fiber for ethanol fermentation. The laboratory-scale fungal saccharification and fermentation process incorporated in situ cellulolytic enzyme induction, which enhanced overall enzymatic hydrolysis of hemi/cellulose components of corn fiber into simple sugars (mono-, di-, and trisaccharides). The yeast fermentation of the hydrolyzate yielded 7.8, 8.6, and 4.9 g ethanol per 100 g corn fiber when saccharified with the white-, brown-, and soft-rot fungi, respectively. The highest ethanol yield (8.6 g ethanol per 100 g initial corn fiber) is equivalent to 35% of the theoretical ethanol yield from starch and cellulose in corn fiber. This research has significant commercial potential to increase net ethanol production per bushel of corn through the utilization of corn fiber. There is also a great research opportunity to evaluate the remaining biomass residue (enriched with fungal protein) as animal feed

Purification and Quality Enhancement of Fuel Ethanol to Produce Industrial Alcohols with Ozonation and Activated Carbon

The total ethanol production capacity in the US just passed 6 billion gals/year. The production process of ethanol from corn includes corn milling, cooking, enzymatic starch conversion, fermentation and distillation. Food-grade alcohol production requires more care and undergoes costly additional purification to remove volatile organic impurities. These impurities could be of health concern and/or impart unpleasant tastes and odors to beverage alcohol. Multiple distillation steps are usually employed. The additional purification of ethanol to obtain food-grade alcohol adds at least $0.30 per gallon in processing costs. In this research, we tested a novel approach to purify fuel grade ethanol to pharmaceutical and beverage grade. The cost of the proposed treatment process is expected to be less than$0.01 per gallon. We have shown that ozone can oxidize a number of undesirable compounds in ethanol. Furthermore, it was demonstrated that adsorption on granular activated carbon can remove many of the ozonolysis byproducts. All chemical and sensory analyses were completed using solid phase microextraction (SPME) to extract volatile organic compounds from ethanol samples and a multidimensional GC-MS-Olfactometry system to identify impurities and the impact of odorous compounds. To date, we confirmed a significant reduction of some impurities with ozone alone. Ozone and granular activated carbon are very effective in purifying fuel ethanol. Also, we designed a purer ozone generating setup. This setup can provide further purification efficiency on this research. This technology will help the corn milling and ethanol industry and provide an opportunity for improving the long-term sustainability of corn growing and processing

Solid Phase Microextraction with On-fiber Derivatization for the Determination of trans-Resveratrol in Iowa Red Wines

Resveratrol (3,5,4’-trihydroxystilbene), found in both grape skin and wines, belongs to the poly-phenol group and has been shown to have cancer-preventing properties, boost cardio-protection and antioxidant activity, inhibition of platelet aggregation and anti-inflammatory activity. In this study, a new method for the trace analysis of trans-resveratrol was developed by using solid phase microextraction with on-fiber silylation derivatization. Multidimensional GC equipped with two columns (a non-polar column and a medium polar column) connected in series, a heart-cut valve and cryogenic focusing capacity and coupled with a mass spectrometric detector with simultaneous scan/SIM mode was employed for the chromatographic separation step which increased separation power allows more accurate quantitative results for trans-resveratrol analysis in the complex matrix-wine. The effects of SPME fiber selection, extraction time as well as extraction temperature were investigated. The optimum conditions of derivatization time and temperature were also studied. Calibration curves for peak area were prepared for the different concentration of extracted cis- and trans-resveratrol. The method detection limit of trans-resveratrol based on SPME on fiber derivatization and multidimensional GC-MS with cryotrap and heart-cut was estimated in this study. The content of total resveratrol of six Iowa red wine samples was determined as well

Ultrasonic Enhanced Liquefaction and Saccharification of Corn for Bio-Fuel Production

Dry grind corn milling does not reach full efficiency of starch conversion to sugars and subsequently to ethanol because of limitations in the milling process. This paper examines the use of high-power ultrasonics to enhance the release of fermentable sugars from milled dry corn. In this work, 20 kHz ultrasonic energy was used to pretreat corn mash prior to enzymatic conversion of corn starch to glucose in a batch-mode. The ultrasonic amplitude was varied from 0, 191 to 320 µm pp . The corn mash was sonicated for 0 (control), 20 and 40 seconds. Other experimental variables that were studied included the effect of temperature and pretreatment sequencing, e.g., ultrasonic pretreatment before and after enzyme addition. It was found that the reaction rate kinetics of the enzymatic reactions increased threefold for sonicated samples. Energy balance (efficiency) analysis indicated that ultrasound pretreatment released twice as much energy (as sugar) when introduced during pretreatment. Based on scanning electron microscopy examination and particle size analysis, the enhancement of the conversion was primarily attributed to particle size reduction, resulting in an increase in the surface area to volume ratio, which in turn increased the available enzymatic reaction sites. One of the most striking findings was that enzymes were not degraded by low level ultrasonication. In addition, the most significant increase in sugar yield was seen when the enzymes were added before ultrasonic pretreatment. Ultrasound has the potential to enhance the ethanol yield from cornstarch and reduce the production cost significantly in commercial dry corn milling ethanol plants

Ozonation-Based Decolorization of Food Dyes for Recovery of Fruit Leather Wastes

Commercial manufacture of fruit leathers (FL) usually results in a portion of the product that is out of specification. The disposition of this material poses special challenges in the food industry. Because the material remains edible and contains valuable ingredients (fruit pulp, sugars, acidulates, etc.), an ideal solution would be to recover this material for product rework. A key practical obstacle to such recovery is that compositing of differently colored wastes results in an unsalable gray product. Therefore, a safe and scalable method for decolorization of FL prior to product rework is needed. This research introduces a novel approach utilizing ozonation for color removal. To explore the use of ozonation as a decolorization step, we first applied it to simple solutions of the commonly used food colorants 2-naphthalenesulfonic acid (Red 40), tartrazine (Yellow 5), and erioglaucine (Blue 1). Decolorization was measured by UV/vis spectrometry at visible wavelengths and with a Hunter colorimeter. Volatile and semivolatile byproducts from ozone-based colorant decomposition were identified and quantified with solid phase microextraction coupled with gas chromatography–mass spectrometry (SPME-GC-MS). Removal of Yellow 5, Red 40 and Blue 1 of about 65%, 80%, and 90%, respectively, was accomplished with 70 g of ozone applied per 1 kg of redissolved and resuspended FL. Carbonyl compounds were identified as major byproducts from ozone-induced decomposition of the food colorants. A conservative risk assessment based on quantification results and published toxicity information of potentially toxic byproducts, determined that ozone-based decolorization of FL before recycling is acceptable from a safety standpoint. A preliminary cost estimate based on recycling of 1000 tons of FL annually suggests a potential of $275,000 annual profit from this practice at one production facility alone

Treatment of Livestock Odor and Pathogens with Ultraviolet Light

Livestock production systems are associated with aerial emissions of odor, volatile organic compounds (VOCs), other gases, and particular matter including airborne pathogens. Control of those emissions is needed to assure compliance with environmental regulations and long-term viability of the industry. The focus of this research is a novel approach to abatement of livestock odor and pathogens utilizing photocatalysis, i.e., UV irradiation in presence of TiO2 as a catalyst. A standard gas generation system was built and tested to generate ten odorous VOCs commonly defining livestock odors. These VOCs included methylmercaptan, ethylmercaptan, dimethylsulfide, butylmercaptan, acetic, propanoic, butyric, and isovaleric acid, p-cresol, and H2S. Our previous research established a reduction of VOCs with UV light only of 60~98% for sulfur VOCs and 91% for p-cresol, but only 20 to 45% removal for volatile fatty acids (VFAs). Titanium dioxide was used in the current research to catalyze UV reactions in the same gas mixtures of VOCs held in a small photoreactor. The reactor was designed to conduct controlled tests with UV light under dynamic (with airflows) conditions that facilitate experiments simulating exhaust from mechanically-ventilated barns. Six 10W lamps with characteristic bands at (185), 254, 312, 365 nm, respectively, and principle output at 254 nm were used as UV source in dynamic system. Solid phase microextraction (SPME) fibers were used to sample VOCs before and after UV treatment and for transfer of samples to a gas chromatography and mass spectrometry olfactometry (GC-MS-O) system. Odor analysis was completed by a forced-choice dynamic-dilution olfactometer in the Olfactometry lab at ISU. Effectiveness of four different treatment options, i.e., UV254, UV185+254, UV254+TiO2, and UV185+254+TiO2 was assessed. Effect of light energy, catalyst presence and light wavelength was evaluated. More than 50% in chemical reduction was found for all VOCs tested with a treatment time of 18.5 second. A linearly positive correlation was found between the percent conversion of tested VOCs and light energy dose. TiO2 showed to greatly improve the treatment effectiveness on VOCs, VFAs in particular, no matter deep UV was used or not. However, when TiO2 was used, deep UV showed very little improvement in degrading VOCs tested, while significant improvement was observed when no TiO2 was used. Total odor reduction of 70% by certain energy level indicated the feasibility of odor mitigation by UV light. Continued work includes simultaneous inactivation of airborne pathogens with UV light

Ultrasonic Pretreatment of Corn Slurry in Batch and Continuous Systems

The effects of ultrasonication of corn slurry, on particle size distribution and enzymatic hydrolysis was studied for the dry-grind mill ethanol industry. Two independent ultrasonic experiments were conducted at a frequency of 20 kHz; in batch and continuous systems. The ground corn slurry (33% m/v) was pumped at flow rates 10-28 L/min in continuous flow experiments, and sonicated at constant amplitude (20µmpeak-to-peak(p-p)). Ultrasonic batch experiments were conducted at varying amplitudes of 192-320µmp-p. After ultrasonication, StargenTM001 enzyme was added to the samples and a short 3h hydrolysis followed. The treated samples were found to yield 2-3 times more reducing sugar compared to the control (untreated) samples. In terms of energy density, the batch ultrasonic system was found to deliver 25-times more energy than the continuous flow systems. Although the experiments conducted in continuous system released less reducing sugar than the batch system, the continuous system was more energy efficient. The particle size of the sonicated corn slurry (both batch and continuous) was reduced relative to the controls (without treatment). The reduction of particle size was directly proportional to the energy input during sonication. The study suggests that both batch and continuous flow ultrasonic systems enhances enzymatic hydrolysis yield, reduces particle size of corn slurry and could be a potential effective pretreatment for corn slurry