Axial mixing in rotating drums using magnetic resonance imaging using bran as a model for solid state fermentations

Magnetic resonance imaging (MRI) is an easily automated, reliable technique to investigate axial mixing within rotating drums. Moist bran can be clearly differentiated from dry bran using MRI allowing a non-segregating tracer for axial mixing. For a 20-cm diameter drum, the axial dispersion coefficient in the particle bed was 0.51 cm s^–2. Axial dispersion is scale-dependent.     

Discrete particle simulations predicting mixing behavior of solid substrate particles in a rotating drum fermenter.

A soft-sphere discrete particle model was used to simulate mixing behavior of solid substrate particles in a slow rotating drum for solid-state fermentation. In this approach, forces acting on and subsequent motion of individual particles can be predicted. The (2D) simulations were qualitatively and quantitatively validated by mixing experiments using video and image analysis techniques. It was found that the simulations successfully predicted the mixing progress as a function of the degree of filling and size of the drum. It is shown that only relatively large, straight baffles perpendicular to the drum wall (67% of the drum radius) increase the mixing performance of the rotating drum. Considering the different aspects of mixing dealt with in this work, it is concluded that the soft sphere discrete particle model can serve as a valuable tool for investigating mixing of solid substrate particles. Finally, it is expected that this model may evolve into a potential tool for design and scale-up of mixed solid-state fermenters.     

Enzymatic production of N-acetyl-D-glucosamine by solid state fermentation of chitinase by Penicillium ochrochloron MTCC 517 using agricultural residues

The optimization studies for production of chitinase were carried out by response surface methodology (RSM) based on statistics experimental design using three substrates, which were wheat, rice and red gram bran. 2⁴ full factorial central composite design was applied to evaluate optimal combinations of variables. These variables were chitin concentration, initial moisture content, inoculum level, and incubation time. The results of second order polynomial showed that all four variables had significant effect on chitinase production. Maximum chitinase activity was recorded for wheat bran (2443.23 U g⁻¹) than rice (1216.65 U g⁻¹) and red gram bran (961.32 U g⁻¹). An overall 3-fold increase in chitinase activity was achieved using optimized strategies of RSM. Growth of the fungus on all bran particles have been visualized by scanning electron microscopy. These results indicated the potential of Penicillium ochrochloron for economical production of chitinase using agricultural residues. TLC and HPLC analysis of colloidal chitin hydrolysate with partially purified chitinases revealed that the major reaction product was monomeric GlcNAc indicating the potential of these enzymes for efficient production of GlcNAc.     

Production of mosquitocidal <Emphasis Type="Italic">Bacillus sphaericus</Emphasis> by solid state fermentation using agricultural wastes

In this study, Bacillus sphaericus NRC 69 was grown in culture media, in which 12 agricultural wastes were tested as the main carbon, nitrogen and energy sources under solid state fermentation. Of the 12 tested agricultural by-products, wheat bran was the most efficient substrate for the production of B. sphaericus mosquitocidal toxins against larvae of Culex pipiens (LC₅₀ 1.2 ppm). Mixtures of tested agricultural wastes separately with wheat bran enhanced the produced toxicity several folds and decreased LC₅₀ between 3.7- and 50-fold in comparison with that of agricultural wastes without mixing. The toxicity of B. sphaericus grown in wheat bran/rice hull at 8/2 (g/g) and wheat bran/barley straw at 1/4 (g/g) showed the same toxicity as that in wheat bran medium (LC₅₀ decreased 17- and 16-fold, in comparison with that in rice hull or barely straw media, respectively). In wheat bran medium, the maximum toxicity of the tested organism obtained at 50% moisture content, inoculum size 84 × 10⁶ CFU/g wheat bran and incubation for 6 days at 30°C. Addition of cheese whey permeate at 10% to wheat bran medium enhanced the toxicity of B. sphaericus NRC 69 about 46%.     

Phosphorylation of Myo-inositol by Isolated Aleurone Particles of Rice

When aleurone particles isolated from rice grains were incubated with ³²P-orthophosphate or ³H-myo-inositol, both radioactivities were incorporated into an acid-stable phosphate ester. As the reaction product, myo-inositol monophosphate was recognized by ion exchange column chromatography. The phosphorylation activity was highest at the bran which corresponded to the aleurone layer. These observations suggest that the phosphorylation site of myo-inositol in the rice grain is the aleurone particles.

The phosphorylation of myo-inositol was enhanced by the existence of ATP. The optimum pH and temperature for the phosphorylation were 7.9 and 30°C, respectively.     

Baffles increase performance of solid-state fermentation in rotating drum bioreactors

Summary Rhizopus oligosporus grew better on wheat bran in a rotating drum when baffles were fitted. The maximum O₂ uptake rates for the baffled and unbaffled runs were 9.0 and 5.7 mmol/min.kg initial dry substrate respectively. The RQ remained at 1.0 throughout the baffled run but varied between 1.0 and 1.2 for the unbaffled run.     

Reduction of grasshopper populations following field application of the fungus Beauveria bassiana

Conidia of the Hyphomycete fungus Beauveria bassiana (Bals.) were applied in an attempt to reduce field populations of grasshoppers, primarily the migratory grasshopper Melanoplus sanguinipes (Fabricius). Dry spores were applied with wheat bran carrier to three fallow fields at a rate of 2.0 × 10¹³ spores ha^?1 in 10 kg bait ha^?1. Examination of culture plates that had been placed in the field to capture spores and of bran carrier with scanning electron microscopy indicated that a substantial portion of the B. bassiana colony—forming units (spores and clumps of spores) did not adhere to the bran and were applied in the field as free particles. Grasshoppers collected from the treated plots at intervals after application were assayed for infection by B. bassiana. The observed rate of mycosis in the treated populations was 70% of those collected after 2 days, declining to 41% by 13 days and 5% by 19 days after application. Analysis of reductions in population density gave results in agreement with the infection data. Treated populations declined 60% and 33% by 9 and 15 days after application respectively. The reductions were significant on both post—treatment sampling dates (p < 0.05) and the three replicated fields gave comparable results. This is the first field demonstration of effectiveness of this fungus as a microbial control agent of grasshoppers.     

Trypsin inhibitor,mineral availability,and performance of broiler chickens fed on diets based on rice bran

Trypsin inhibitor in rice bran was inactivated by moist heat, but not by dry heating or treatments with 0.1% H₂SO₄, 0.1% NaOH or 0.1% NaCl. Heating rice bran could not improve its growth promotion value in the diet of broilers, which was related to the feed intake. Groundnut meal was the major protein supplement in the diets. Rice bran diets did not affect weight of pancreas (1.45–1.50 g/kg body weight). Use of ⁴⁵Ca revealed that availability of calcium on a rice bran diet was lower than on a maize-based diet. A similar effect on ⁵⁹Fe-availability was noted, although this result needs confirmation. Lack of differences in weight of thyroid glands and uptake of ¹³¹I by thyroids of birds on maize- and rice bran-based diets indicated the absence of any goitrogenic substance in the rice bran.     

Numerical simulation and deacidification of nanomagnetic enzyme conjugate in a liquid–solid magnetic fluidized bed

The conventional deacidification method is difficult to achieve a better refining effect due to the high acid value in the rice bran crude oil, and the enzymatic esterification deacidification method can effectively reduce the acid value without generating chemical waste. In this study, the free lipase was immobilized on a magnetic polymer carrier Fe₃O₄/SiOx-g-P (GMA: glycidyl methacrylate) to obtain a immobilized lipase with a particle size of 105.30 ± 1.1 nm and an enzyme activity of 6580 ± 9.6 PLU/g (PLU: enzyme activity unit). Based on the batch deacidification process parameters, a multi-stage magnetic fluidized bed continuous circulation deacidification system was designed, and then the motion law of nanomagnetic immobilized lipase particles in liquid–solid magnetic fluidized bed was simulated by computer. When the iterative step was 5 × 10⁻⁵ s, the open porosity of the porous plate was 35.0%, the rice bran oil flow rate was 3.0 mm/s, and the magnetic field strength was 25.0 mT, which was beneficial to the deacidification reaction of rice bran oil. Under the conditions of magnetic immobilized lipase dosage of 4.0%, the phytosterol dosage of 22.0%, the molecular sieve dosage of 10%, the esterification temperature of 78.0 °C and the FFA (free fatty acid) content in rice bran oil decreased to 1.5%, after 48 h of reaction. The conversion rate is 92.8%, which provides a theoretical basis for the subsequent guidance of magnetic fluidized bed enzymatic continuous deacidification.     

Identifying resuspended particles using isotope ratios

Three simple methods were developed to estimate the proportion of particles in lake water derived from resuspended material. These techniques use the different distributions of long and short-lived radioisotopes sorbed onto particles and were tested in the three basins of Lake Erie using ⁷Be, ¹³⁷Cs and ²¹⁰Po/²¹⁰Pb.While the concentration of ²¹⁰Po on particles did not vary significantly in the lake, resuspended particles were characterized by high concentrations of ¹³⁷Cs and low concentrations of ⁷Be. The distribution of these radioisotopes is consistent with a simple mixing model in which the fraction of particles in the lake water derived from resuspension ranged from 8% to about 100%. Higher concentrations of resuspended particles were found in deeper samples from the nepheloid layer and in the shallow western basin where thermal stratification was very weak.     

Production of high activity thermostable phytase from thermotolerant Aspergillus niger in solid state fermentation

The thermotolerant fungus, Aspergillus niger NCIM 563, was used for production of extracellular phytase on agricultural residues: wheat bran, mustard cake, cowpea meal, groundnut cake, coconut cake, cotton cake and black bean flour in solid state fermentation (SSF). Maximum enzyme activity (108 U g⁻¹ dry mouldy bran, DMB) was obtained with cowpea meal. During the fermentation phytic acid was hydrolysed completely with a corresponding increase in biomass and phytase activity within 7 days. Phosphate in the form of KH₂PO₄ (10 mg per 100 g of agriculture residue) increased phytase activity. Among various surfactants added to SSF, Trition X-100 (0.5%) exhibited a 30% increase in phytase activity. The optimum pH and temperature of the crude enzyme were 5.0 and 50°C respectively. Phytase activity (86%) was retained in buffer of pH 3.5 for 24 h. The enzyme retained 75% of its activity on incubation at 55°C for 1 h. In the presence of 1 mM K⁺ and Zn²⁺, 95% and 55% of the activity were retained. Scanning electron microscopy showed a high density growth of fungal mycelia on wheat bran particles during SSF. Journal of Industrial Microbiology & Biotechnology (2000) 24, 237–243. Received 07 June 1999/ Accepted in revised form 18 December 1999     

Solid-state fermentation in rotating drum bioreactors: operating variables affect performance through their effects on transport phenomena

Aspergillus oryzae ACM 4996 was grown on an artificial gel-based substrate and on steamed wheat bran during solid-state fermentations in 18.7 L rotating drum bioreactors. For gel fermentations fungal growth decreased as rotational speed increased, presumably due to increased shear. For wheat bran fermentations fungal growth improved under agitated compared to static culture conditions, due to superior heat and mass transfer. We conclude that the effects of operational variables on the performance of SSF bioreactors are mediated by their effects on transport phenomena such as mixing, shear, heat transfer, and mass transfer within the substrate bed. In addition, the substrate characteristics affect the need for and the rates of these transport processes. Different transport phenomena may be rate limiting with different substrates. This work improves understanding of the effects of bioreactor operation on SSF performance.     

Three-dimensional simulation of grain mixing in three different rotating drum designs for solid-state fermentation

A previously published two-dimensional discrete particle simulation model for radial mixing behavior of various slowly rotating drums for solid-state fermentation (SSF) has been extended to a three-dimensional model that also predicts axial mixing. Radial and axial mixing characteristics were predicted for three different drum designs: (1) without baffles; (2) with straight baffles; and (3) with curved baffles. The axial mixing behavior was studied experimentally with video- and image-analysis techniques. In the drum without baffles and with curved baffles the predicted mixing behavior matched the observed behavior adequately. The predicted axial mixing behavior in the drum with straight baffles was predicted less accurately, and it appeared to be strongly dependent on particle rotation, which was in contrast to the other drum designs. In the drum with curved baffles complete mixing in the radial and axial direction was achieved much faster than in the other designs; that is, it was already achieved after three to four rotations. This drum design may therefore be very well suited to SSF. It is concluded that discrete particle simulations provide valuable detailed knowledge about particle transport processes, and this may help to understand and optimize related heat and mass transfer processes in SSF.     

The effects of bioturbation on particle redistribution in Mediterranean coastal sediment. Preliminary results

In order to quantify bioturbation processes in a coastal Mediterranean ecosystem, experiments were performed to determine sediment mixing rates resulting from macrobenthos activity. Particle flux was measured in situ for 22 days using luminophores, which are colored sediment particles with sizes ranging from 10 to 200 µm.In sediment depths from 0–5 cm, particle mixing was intensive due to high macrobenthos abundance. A small quantity of luminophores was transported down to a depth of 14 ± 2 cm, where the macrofauna was represented principally by Polychetes. In a control experimental structure — without benthic fauna — no transfer of luminophores into the sediment was recorded.Sediment particle mixing measured in the ecosystem studied is intensive, and is the result of high macrobenthos activity. Different mixing modes occur with scales and rates depending on the organisms present. The luminophore profile resulting from bioturbation processes is explained by an intensive bioadvection sediment mixing added to a biodiffusive mixing with an order of magnitude of 10^–6 cm² s^–1. Tracer accumulations between 1 and 2 ± 1 cm and between 4 and 5 ± 1 cm are attributed to bioadvection activity of two or more distinct populations. Studies over a larger time scale have been undertaken to monitor developments in the observed subsurface maxima.     

The potential for establishment of axial temperature profiles during solid-state fermentation in rotating drum bioreactors

The mixing and heat transfer phenomena within rotating drum bioreactors (RDBs) used for solid-state fermentation processes are poorly studied. The potential for the establishment of axial temperature gradients within the substrate bed was explored using a heat transfer model. For growth of Aspergillus oryzae on wheat bran within a 24 L RDB with air at a superficial velocity of 0.0023 m s(-1) and 15% relative humidity, the model predicts an axial gradient between the air inlet and outlet of 2 degrees C during rapid growth, compared to experimental axial temperature gradients of between 1 and 4 degrees C. Undesirably high temperatures occur throughout the bed under these operating conditions, but the model predicts that good temperature control can be achieved using humid air (90% relative humidity) at superficial velocities of 1 m s(-1) for a 204 L RDB. For a 2200 L RDB, good temperature control is predicted with superficial velocities as low as 0.4 m s(-1) with the airflow being switched from 90% to 15% relative humidity whenever the temperature at the outlet end of the drum exceeds the optimal temperature for growth. This work suggests that significant axial temperature gradients can arise in those RDBs that lack provision for axial mixing. It is therefore advisable to use angled lifters within RDBs to promote axial mixing.     

Cyclosporin-A production by Tolypocladium inflatum using solid state fermentation

Tolypocladium inflatum strains are known to produce Cyclosporin-A under submerged culture conditions. In the present study solid state fermentation was used to produce Cyclosporin-A. Tolypocladium inflatum strains when grown on moist wheat bran produced 310–459 mg of Cyclosporin-A kg of bran⁻¹. Tolypocladium inflatum ATCC 34921 which produced 459 mg of Cyclosporin-A kg of bran⁻¹ was improved to produce 1031±27 mg of Cyclosporin-A kg⁻¹ of bran, by subjecting the spores to different mutagenic treatments. The mutated strain, designated Tolypocladium inflatum DRCC 106, produced 4843 mg kg⁻¹ of bran under optimum fermentation conditions in 10 days when grown on wheat bran medium containing millet flour 20%, jowar flour 10%, zinc sulphate 0·15%, ferric chloride 0·25% and cobaltous chloride 0·05%. An inoculum of 60% initial moisture content 70%, initial bran pH 2·0 and incubation temperature 25°C were found to be optimal. Cyclosporin-A thus obtained was purified by solvent extraction, followed by column chromatography. The isolated product complies with the United States Pharmacopoeia specifications.     

Spore production ofPenicillium roqueforti in fermentors filled with buckwheat seeds: batch and semi-continuous cultivation

Summary The behaviour of a drum fermentor and a column fermentor during the sporulation ofPenicillium roqueforti on buckwheat seeds is presented. The main problem encountered during the course of a cultivation is the free water released (about 0.1 ml/g dry matter) which must be removed from the medium. The rotation of the drum fermentor may disturb the growth and the sporulation. The column fermentor thus represents the best way to perform batch cultivation of the fungus: 10⁹ external spores/g dry matter are obtained.Semi-continous cultivation, with sequential emptying and filling, is performed in 1-liter bottles. This kind of cultivation may give a maximal average productivity close to 9.2·10⁶ external spores/g dry matter per hour. A drum fermentor, rotading only when emptying and filling, could represent an alternative to perform this kind of cultivation.     

Potential of passive acoustic recording for monitoring invasive species: freshwater drum invasion of the Hudson River via the New York canal system

We conducted a preliminary passive acoustic survey of the occurrence of freshwater drum, Aplodinotus grunniens, in the New York State Canal System (NYSCS) to demonstrate the usefulness of underwater sound monitoring in invasive species studies. Data from known populations of freshwater drum in Dale Hollow Reservoir and J. Percy Priest Lake in Tennessee and Lake Champlain in New York were used to validate freshwater drum call characteristics. Similar to more well studied marine members of the Sciaenidae, freshwater drum calls are composed of highly variable trains of 1–119 knocks call^?1 (mean = 25 knocks call^?1), a mean knock period of 33 knocks s^?1, mean peak frequency of 400 Hz, and mean duration of 0.8 s. The occurrence of drum chorus calls at many locations within the NYSCS indicates likely spawning throughout the system, and suggests the possibility that individuals have invaded the Hudson River from native populations of Lake Champlain, Lake Erie, and Lake Ontario. We point out that the species has been excluded from the east coast of North America throughout history by geographic barriers, and it would have been impossible for the species to gain entrance to the Hudson without the NYSCS, or direct introduction, and thus it is a true invasive which will likely have a dramatic impact on the Hudson River ecosystem. We suggest that freshwater drum most likely also invaded Lakes Oneida, Onondaga, Cayuga and Seneca through the NYSCS. We conclude that passive acoustic surveys are a highly effective non-invasive tool to monitor the distribution of soniferous invasive organisms in aquatic systems, and promise to be especially useful in documenting the future spread of freshwater drum in the Hudson River system.     

Production of aryl metabolites in solid-state fermentations of the white-rot fungus Bjerkandera adusta

Bjerkandera adusta produced aromatic compounds such as benzaldehyde (bitter almond aroma), benzyl alcohol and benzoic acid from L-phenylalanine (3 g kg^–1). Two supports for the fungus, wheat bran (organic support) and Perlite (mineral support), gave optimal production with water contents of 66% and 60%, respectively. Benzyl alcohol (4.53 g kg^–1) and benzaldehyde (1.56 g kg^–1) were produced after 4 days on wheat bran respectively with 20 and 30 g L-phenylalanine kg^–1. Aryl alcohol oxidase activity, which oxidises benzyl alcohol to benzaldehyde, was only detected when the fungus was grown on wheat bran, the support which promotes the most benzaldehyde production. Results are compared with those obtained in submerged liquid cultures.     

Importance of timing,spore concentrations,and levels of spore carrier in applications of Nosema locustae (Microsporida: Nosematidae) for control of grasshoppers

In a study of microbial control of grasshoppers, Nosema locustae was applied to 10-acre plots in 2 replications of 24 treatment combinations in which the factors were (1) times of applications: 4 applications spaced over 22 days; (2) concentrations of spores: 1, 30, and 900 spores/in²; and (3) levels of the spore carrier: 1 and 4 lb wheat bran/acre. The concentrations of spores had the most effect in reducing the densities of grasshoppers and the incidence of infection among the survivors at the last sampling (coincided with the initiation of oviposition), the average reduction in density attributed to application of 1 spore/in² was 21%, that attributed to 30 spores/in² was 46%, and that attributed to 900 spores/in² was 73%. The first and second applications caused the greatest reductions in density; the second, third, and fourth applications produced the highest incidence of infections. Also, a higher incidence of infection was observed among grasshoppers from plots treated with 30 spores/in² on 1 lb bran/acre than from plots treated with 30 spores/in² on 4 lb of bran/acre. Therefore, a ratio of about 0.63–0.94 billion spores/lb bran applied at a rate of 1–1.5 lb/acre (= 100–150 spores/in²) at the time when the principal early summer species are third-instar nymphs would have resulted in overall reductions in density of 50–60%, with 35–50% of the survivors sufficiently infected so that fecundity would probably be affected. The reductions and incidence of infections would be higher in species that readily accept and use wheat bran, among which are some of the more economically important species of grasshoppers.