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A L Pometto

Publications and source records attributed to A L Pometto.

18 recordsLinked to original sources
PubMed2001

Evaluation of plastic-composite supports in repeated fed-batch biofilm lactic acid fermentation by Lactobacillus casei.

A customized stirred-tank biofilm reactor was designed for plastic-composite supports (PCS). In repeated-batch studies, the PCS-biofilm reactors outperformed the suspended-cell reactors by demonstrating higher lactic acid productivities (2.45 g l(-1) h(-1) vs 1.75 g l(-1) h(-1)) and greater glucose consumption rates (3.27 g l(-1) h(-1) vs 2.09 g l(-1) h(-1)). In the repeated fed-batch studies, reactors were spiked periodically with concentrated glucose (75%) to maintain a concentration of approximately 80 g of glucose l(-1) in the bioreactor. In suspended-cell fermentations with 10 g of yeast extract (YE) l(-1) and zero, one, two, and three glucose spikes, the lactic acid productivities were 2.64, 1.58, 0.80, and 0.62 g l(-1) h(-1), respectively. In comparison, biofilm reactors with 7 g of YE l(-1) and zero, one, two, and three glucose spikes achieved lactic acid productivities of 4.20, 2.78, 0.66, and 0.94 g l(-1) h(-1), respectively. The use of nystatin (30 U ml(-1)) subdued the contaminating yeast population with no effect on the lactic acid productivity of the biofilm reactors, but it did affect productivity in the suspended-cell bioreactor. Overall, in repeated fed-batch fermentations, the biofilm reactors consistently outperformed the suspended-cell bioreactors, required less YE, and produced up to 146 g of lactic acid l(-1) with 7 g of YE l(-1), whereas the suspended-cell reactor produced 132 g l(-1) with 10 g of YE l(-1).

Biofilms↗
PubMed2001

Continuous lactic acid fermentation using a plastic composite support biofilm reactor.

An immobilized-cell biofilm reactor was used for the continuous production of lactic acid by Lactobacillus casei subsp. rhamnosus (ATCC 11443). At Iowa State University, a unique plastic composite support (PCS) that stimulates biofilm formation has been developed. The optimized PCS blend for Lactobacillus contains 50% (wt/wt) agricultural products [35% (wt/wt) ground soy hulls, 5% (wt/wt) soy flour, 5% (wt/wt) yeast extract, 5% (wt/wt) dried bovine albumin, and mineral salts] and 50% (wt/wt) polypropylene (PP) produced by high-temperature extrusion. The PCS tubes have a wall thickness of 3.5 mm, outer diameter of 10.5 mm, and were cut into 10-cm lengths. Six PCS tubes, three rows of two parallel tubes, were bound in a grid fashion to the agitator shaft of a 1.2-1 vessel for a New Brunswick Bioflo 3000 fermentor. PCS stimulates biofilm formation, supplies nutrients to attached and suspended cells, and increases lactic acid production. Biofilm thickness on the PCS tubes was controlled by the agitation speed. The PCS biofilm reactor and PP control reactor achieved optimal average production rates of 9.0 and 5.8 g l(-1) h(-1), respectively, at 0.4 h(-1) dilution rate and 125-rpm agitation with yields of approximately 70%.

Biofilms↗
PubMed1999

Enhanced organically bound selenium yeast production by fed-batch fermentation.

This study describes a fed-batch fermentation protocol for enhanced production of Saccharomyces cerevisiae containing organically bound selenium. Two levels of sodium selenate concentrations were applied as either a single dose or continuous addition. Fermentations with high sodium selenate (63.2 g/L in cane molasses feeding medium) demonstrated 24 g/L of biomass with 1382 microg of selenium/g of dry biomass for single-dose addition and 40 g/L of biomass with 1491 microg of selenium/g of dry biomass for continuous addition. Low selenium concentration (31.6 g/L in cane molasses feeding medium) demonstrated higher biomass concentration with higher selenium level; 37 g/L of biomass with 2846 microg of selenium/g of dry biomass and 45 g/L of biomass with 2495 microg of selenium/g of dry biomass for single-dose and continuous addition, respectively. Also, two adapted S. cerevisiae strains were evaluated in fed-batch fermentation. A single dose of low concentration demonstrated >3000 microg of selenium/g of dry biomass, but biomass concentration was lower (< or =32 g/L) for these adapted strains.

Arsenicals↗
PubMed1999

Production of organically bound selenium yeast by continuous fermentation.

This paper describes a protocol for incorporation of sodium selenite or sodium selenate into Saccharomyces cerevisiae biomass by continuous fermentation in a medium with minimal sulfur and methionine concentrations. Selenium incorporation was followed by atomic absorption analysis and methylene blue reduction time (MBRT). Continuous fermentation at 0.2 h(-1) dilution rate and sodium selenite addition gradient up to 0.69 g/L of Na(2)SeO(3) yielded 1. 89 g/L of biomass with 1904 microg of selenium/g of dry biomass. However, MBRT was 0.1 min, which indicated that the majority of selenium was in the inorganic form. On the other hand, continuous fermentation at 0.2 h(-1) dilution rate and sodium selenate gradient up to 0.28 g/L of Na(2)SeO(4) yielded 0.76 g/L of dry biomass with 687 microg of selenium/g of dry biomass, and MBRT was 26 min, which indicated a high concentration of organically bound selenium. Overall, the results indicate a Se/S ratio of 3.9:1 and a dry biomass/Se ratio of 5.5:1 as optimal for continuous production of organically bound selenium.

Arsenicals↗
PubMed1997

Ethanol production by Saccharomyces cerevisiae in biofilm reactors.

Biofilms are natural forms of cell immobilization in which microorganisms attach to solid supports. At ISU, we have developed plastic composite-supports (PCS) (agricultural material (soybean hulls or oat hulls), complex nutrients, and polypropylene) which stimulate biofilm formation and which supply nutrients to the attached microorganisms. Various PCS blends were initially evaluated in repeated-batch culture-tube fermentation with Saccharomyces cerevisiae (ATCC 24859) in low organic nitrogen medium. The selected PCS (40% soybean hull, 5% soybean flour, 5% yeast extract-salt and 50% polypropylene) was then used in continuous and repeated-batch fermentation in various media containing lowered nitrogen content with selected PCS. During continuous fermentation, S. cerevisiae demonstrated two to 10 times higher ethanol production in PCS bioreactors than polypropylene-alone support (PPS) control. S. cerevisiae produced 30 g L-1 ethanol on PCS with ammonium sulfate medium in repeated batch fermentation, whereas PPS-control produced 5 g L-1 ethanol. Overall, increased productivity in low cost medium can be achieved beyond conventional fermentations using this novel bioreactor design.

Biofilms↗
PubMed1997

Ingredient selection for plastic composite supports for L-(+)-lactic acid biofilm fermentation by Lactobacillus casei subsp. rhamnosus.

Plastic composite supports containing 50% agricultural products (oat hulls, soybean hulls, yeast extract, soybean flour, dried bovine erythrocytes, bovine albumin, and/or mineral salts) and 50% (wt/wt) polypropylene were produced by high-temperature twin-screw extrusion. The research employed two half sets of a five-factorial fractional design (2(5 - 1)) to evaluate the effects of different agricultural components on the properties of the plastic composite supports and to select the best plastic composite support formulation for lactic acid fermentation. The biofilm population was affected by the contact angle and relative hydrophobicity of the supports (r = 0.79 to 0.82). Lactic acid was produced by the suspended cells (r = 0.96) and the biofilm on the plastic composite support discs (r = 0.85). Incorporation of yeast extract into plastic composite supports enhanced growth of free and attached cells in minimal medium (P < 0.0001). The presence of soybean hulls, yeast extract, or mineral salts in plastic composite supports produced less hydrophobic supports (P < 0.0001) and enhanced cell attachment (P < 0.03). Under all conditions, suspended-cell and polypropylene disc controls gave negligible lactic acid production and cell density. Plastic composite supports containing soybean hulls, yeast extract, soybean flour, bovine albumin, and mineral salts gave the highest biofilm population (2.3 x 10(9) CFU/g of support), cell density (absorbance of 1.8 at 620 nm), and lactic acid concentration (7.6 g/liter) in minimal medium.

Animals↗
PubMed1997

Optimization of L-(+)-lactic acid production by ring and disc plastic composite supports through repeated-batch biofilm fermentation.

Four customized bioreactors, three with plastic composite supports (PCS) and one with suspended cells (control), were operated as repeated-batch fermentors for 66 days at pH 5 and 37 degrees C. The working volume of each customized reactor was 600 ml, and each reactor's medium was changed every 2 to 5 days for 17 batches. The performance of PCS bioreactors in long-term biofilm repeated-batch fermentation was compared with that of suspended-cell bioreactors in this research. PCS could stimulate biofilm formation, supply nutrients to attached and free suspended cells, and reduce medium channelling for lactic acid production. Compared with conventional repeated-batch fermentation, PCS bioreactors shortened the lag time by threefold (control, 11 h; PCS, 3.5 h) and sixfold (control, 9 h; PCS, 1.5 h) at yeast extract concentrations of 0.4 and 0.8% (wt/vol), respectively. They also increased the lactic acid productivity of Lactobacillus casei subsp. rhamnosus (ATCC 11443) by 40 to 70% and shortened the total fermentation time by 28 to 61% at all yeast extract concentrations. The fastest productivity of the PCS bioreactors (4.26 g/liter/h) was at a starting glucose concentration of 10% (wt/vol), whereas that of the control (2.78 g/liter/h) was at 8% (wt/vol). PCS biofilm lactic acid fermentation can drastically improve the fermentation rate with reduced complex-nutrient addition.

Bacteriological Techniques↗
PubMed1996

Fumonisin B1 production by Fusarium proliferatum strain M5991 in a modified Myro liquid medium.

Fusarium proliferatum strain M5991 cultures were grown in shake flasks containing modified Myro (MM) medium (MgSO4 reduced to 0.5 g/L) plus 0, 0.25, 0.50, 0.75, 1.00, or 1.25% (v/v) hot-water and corn-hull-extract (CHE) for 69 days. After 4 days of incubation, shake flask liquid cultures with 0.75, 1.00, and 1.25% (v/v) CHE showed a reduction in pH from 6.0 to 2.6 and consumed sucrose at > 6.3 g/L/d. After 69 days of incubation, the same shake flask cultures produced over 7.8 g/L cell mass and over 990 mg/L fumonisin B1 (FB1). A minimum CHE level of 0.75% was recommended for enhanced FB1 production by F. proliferatum strain M5991. During three serial (10, 12, and 12 L) batch fermentations in MM medium + 1.00% (v/v) CHE (first batch only), F. proliferatum strain M5991 produced FB1 concentrations of 619, 659, and 375 mg/L after 35, 47, and 52 days of incubation, respectively. By analysis, a total yield of 20 g FB1 was obtained from three serial batch fermentations.

Analysis of Variance↗
PubMed1996

Continuous ethanol production by Zymomonas mobilis and Saccharomyces cerevisiae in biofilm reactors.

Continuous ethanol fermentations were performed in duplicate for 60 days with Zymomonas mobilis ATCC 331821 or Saccharomyces cerevisiae ATCC 24859 in packed-bed reactors with polypropylene or plastic composite-supports. The plastic composite-supports used contained polypropylene (75%) with ground soybean-hulls (20%) and zein (5%) for Z. mobilis, or with ground soybean-hulls (20%) and soybean flour (5%) for S. cerevisiae. Maximum ethanol productivities of 536 g L-1 h-1 (39% yield) and 499 g L-1 h-1 (37% yield) were obtained with Z. mobilis on polypropylene and plastic composite-supports of soybean hull-zein, respectively. For Z. mobilis, an optimal yield of 50% was observed at a 1.92 h-1 dilution rate for soybean hull-zein plastic composite-supports with a productivity of 96 g L-1 h-1, whereas with polypropylene-supports the yield was 32% and the productivity was 60 g L-1 h-1. With a S. cerevisiae fermentation, the ethanol production was less, with a maximum productivity of 76 g L-1 h-1 on the plastic composite-support at a 2.88 h-1 dilution rate with a 45% yield. Polypropylene-support bioreactors were discontinued due to reactor plugging by the cell mass accumulation. Support shape (3-mm chips) was responsible for bioreactor plugging due to extensive biofilm development on the plastic composite-supports. With suspension-culture continuous fermentations in continuously-stirred benchtop fermentors, maximum productivities of 5 g L-1 h-1 were obtained with a yield of 24 and 26% with S. cerevisiae and Z. mobilis, respectively. Cell washout in suspension-culture continuous fermentations was observed at a 1.0 h-1 dilution rate. Therefore, for continuous ethanol fermentations, biofilm reactors out-performed suspension-culture reactors, with 15 to 100-fold higher productivities (g L-1 h-1) and with higher percentage yields for S. cerevisiae and Z. mobilis, respectively. Further research is needed with these novel supports to evaluate different support shapes and medium compositions that will permit medium flow, stimulate biofilm formation, reduce fermentation costs, and produce maximum yields and productivities.

Biofilms↗
PubMed1992

Production of an extracellular polyethylene-degrading enzyme(s) by Streptomyces species.

Extracellular culture concentrates were prepared from Streptomyces viridosporus T7A, Streptomyces badius 252, and Streptomyces setonii 75Vi2 shake flask cultures. Ten-day-heat-treated (70 degrees C) starch-polyethylene degradable plastic films were incubated with shaking with active or inactive enzyme for 3 weeks (37 degrees C). Active enzyme illustrated changes in the films' Fourier transform infrared spectra, mechanical properties, and polyethylene molecular weight distributions.

Fourier Analysis↗
PubMed1990

Lignin-solubilizing ability of actinomycetes isolated from termite (Termitidae) gut.

The lignocellulose-degrading abilities of 11 novel actinomycete strains isolated from termite gut were determined and compared with that of the well-characterized actinomycete, Streptomyces viridosporus T7A. Lignocellulose bioconversion was followed by (i) monitoring the degradation of [14C]lignin- and [14C]cellulose-labeled phloem of Abies concolor to 14CO2 and 14C-labeled water-soluble products, (ii) determining lignocellulose, lignin, and carbohydrate losses resulting from growth on a lignocellulose substrate prepared from corn stalks (Zea mays), and (iii) quantifying production of a water-soluble lignin degradation intermediate (acid-precipitable polymeric lignin). The actinomycetes were all Streptomyces strains and could be placed into three groups, including a group of five strains that appear superior to S. viridosporus T7A in lignocellulose-degrading ability, three strains of approximately equal ability, and three strains of lesser ability. Strain A2 was clearly the superior and most effective lignocellulose decomposer of those tested. Of the assays used, total lignocellulose weight loss was most useful in determining overall bioconversion ability but not in identifying the best lignin-solubilizing strains. A screening procedure based on 14CO2 evolution from [14C-lignin]lignocellulose combined with measurement of acid-precipitable polymeric lignin yield was the most effective in identifying lignin-solubilizing strains. For the termite gut strains, the pH of the medium showed no increase after 3 weeks of growth on lignocellulose. This is markedly different from the pattern observed with S. viridosporus T7A, which raises the medium pH considerably. Production of extracellular peroxidases by the 11 strains and S. viridosporus T7A was followed for 5 days in liquid cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales↗
PubMed1985

L-Phenylalanine and L-tyrosine catabolism by selected Streptomyces species.

L-Phenylalanine and L-tyrosine were completely catabolized through homogentisate by Streptomyces setonii 75Vi2 but only partially degraded by Streptomyces badius 252, Streptomyces sioyaensis P5, Streptomyces viridosporus T7A, and Streptomyces sp. strain V7. Intermediates of catabolism were confirmed by thin-layer, gas, and high-pressure liquid chromatography. Homogentisate 1,2-dioxygenase was present in all cell extracts.

Phenylalanine↗
PubMed1983

Whole-cell bioconversion of vanillin to vanillic acid by Streptomyces viridosporus.

A two-step batch fermentation-bioconversion of vanillin (4-hydroxy-3-methoxybenzaldehyde) to vanillic acid (4-hydroxy-3-methoxybenzoic acid) was developed, utilizing whole cells of Streptomyces viridosporus T7A. In the first step, cells were grown in a yeast extract-vanillin medium under conditions where cells produced an aromatic aldehyde oxidase. In the second step, vanillin was incubated with the active cells and was quantitatively oxidized to vanillic acid which accumulated in the growth medium. Vanillic acid was readily recovered from the spent medium by a combination of acid precipitation and ether extraction at greater than or equal to 96% molar yield and upon recrystallization from glacial acetic acid was obtained in greater than or equal to 99% purity.

Biotransformation↗
PubMed1983

Metabolism of cinnamic, p-coumaric, and ferulic acids by Streptomyces setonii.

Streptomyces setonii strain 75Vi2 was grown at 45 degrees C in liquid media containing yeast extract and trans-cinnamic acid, p-coumaric acid, ferulic acid, or vanillin. Gas chromatography, thin-layer chromatography, and mass spectrometry showed that cinnamic acid was catabolized via benzaldehyde, benzoic acid, and catechol; p-coumaric acid was catabolized via p-hydroxybenzaldehyde, p-hydroxybenzoic acid, and protocatechuic acid; ferulic acid was catabolized via vanillin, vanillic acid, and protocatechuic acid. When vanillin was used as the initial growth substrate, it was catabolized via vanillic acid, guaiacol, and catechol. The inducible ring-cleavage dioxygenases catechol 1,2-dioxygenase and protocatechuate 3,4-dioxygenase were detected with an oxygen electrode in cell-free extracts of cultures grown in media with aromatic growth substrates and yeast extract.

Cinnamates↗
PubMed1981

Streptomyces setonii: catabolism of vanillic acid via guaiacol and catechol.

Streptomyces setonii (strain 75Vi2) was grown at 45 degrees C in liquid media containing simple aromatic compounds as principal carbon sources. Thin-layer chromatography, UV spectrophotometry, and gas chromatography were used to show that S. setonii converted benzoic acid, guaiacol, and vanillic acid to catechol; p-hydroxybenzoic acid to protocatechuic acid; and m-hydroxybenzoic acid to gentisic acid. Presence of the ring-cleavage enzymes catechol 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, and gentisate 2,3-dioxygenase was shown both by O2 uptake in ring-cleavage reactions catalyzed by cell-free extracts and by changes in UV spectra that indicated the presence of specific ring-cleavage products. A unique feature of this strain was its catabolism of vanillic acid by of guaiacol and catechol, using a pathway that had not been confirmed previously.

Benzoates↗
PubMed1977

Degradation of natural and Kraft lignins by the microflora of soil and water.

The comparative rates of microbial degradation of 14C-lignin-labeled lignocelluloses and 14C-Kraft lignins were investigated using selected soil and water samples as sources of microorganisms. Natural lignocelluloses containing 14C primarily in their lignin components were prepared by feeding plants uniformly labeled L-[14C]phenylalanine through their cut stems. 14C-Kraft lignins were prepared by pulping lignin-labeled lignocelluloses. Rates of lignin biodegradation were determined by monitoring 14CO2 evolution from incubation mixtures over incubation periods of up to 1000 h. Observed rates of lignin degradation were slow in all cases. Kraft lignins appeared more resistant to microbial attack than natural lignins, even though they were decomposed more rapidly during the first 100-200 h of incubation. Similar degradation patterns were observed in both soil and water. Individual samples, however, varied greatly in their overall rates of degradation of either lignin type. A Kraft-lignin preparation was separated into a variety of molecular weight fractions by column chromatography on LH-20 Sephadex and the biodegradability of the different molecular weight fractions determined. The lower molecular weight fractions of the Kraft lignin were decomposed at a significantly faster rate by the microflora of soil than were the fractions of higher molecular weight.

Bacteria↗