Experimental approaches to a rapid ethanol fermentation of glucose by aZymomonas mobilis strain

Rapid ethanol fermentation is defined as a fermentation in which the ethanol content increases from 0 to 94.8 g 1^–1 in 6 horless. To achieve this by the fermentation of glucose withZymomonas mobilis, the initial biomass concentration must be at least 20 g dry wt 1^–1 and that of the substrate must not exceed 150 to 200 g 1^–1 during fermentation. The best results were obtained with a medium containing initielly 16% of the total sugar with the remaining glucose being added continuously, after 20 min of incubation, over 5 h at a rate of 0.21 g/min. After 6 h, ethanol reached 102 g 1^–1, the volumetric productivity was 17g ethanol 1^–1 h^–1 and the yield 79.8 or 88% of the theoretical value, calculated according to the total fed or the consumed glucose, respectively.

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Résumé Quand la concentration d'alcool produit par fermentation monte de 0 a 94.8 g 1^–1 dans un delai de 6 h ou moins, on appelle a cette fermentation, alcoolique rapide. Dans le present travail on a determiné les conditions pour avoir une fermentation alcoolique rapide a partir de glucose, utilisant une souche deZymomonas mobilis. On a trouvé que la concentration initiale de biomasse doit etre au moins 20 g de céllules poids sec/litre et la concentration du sucre doit se mantenir au dessous de 150–200 g 1^–1 pendant la fermentation. Les meilleurs résultats qu'on a eu ont été avec un milieu qu'avait au dessous de 150–200 g 1^–1 pendant la fermentation. Les meilleurs résultats qu'on a eu ont été avec un milieu qu'avait au commencement 1/6 du sucre total et l'excedent a été ajouté apres 20 minutes pendant 5 heures en quantités de 0.21 g/min. Aux 6 h la concentration d'alcool estarrivé a 102 g 1^–1, le rendement calculé sur le sucre utilisé était 88% du théorique (79.8% du sucre alimenté) et la production volumétrique 17 g ethanol 1^–1 h^–1.

     

Production of ethanol from starch by free and immobilized Candida tropicalis in the presence of alpha-amylase

Candida tropicalis is a potentially useful organism for the commercial production of ethanol as it is capable of fermenting starch at a low rate. To enhance this carbon source utilization and increase the rate of alcohol production, we pretreated corn soluble starch with alpha-amylase. Starch liquefaction was sufficient to drive the fermentation and to convert 96% substrate to ethanol. Indeed, in the presence of exogenous alpha-amylase, 9% (w/v) soluble starch was converted to 43.1g ethanol/l in 65 h with a productivity of 0.65 g/l h. Thus, bio-ethanol production using free and calcium alginate-immobilized C. tropicalis does not require the saccharification step. Furthermore, fed-batch fermentation by free C. tropicalis cells increased the final concentration to 56 g ethanol/l, reaching published values for Saccharomyces cerevisiae recombinant strains expressing both alpha-amylase and glucoamylase.     

Degradation of 2-methylnaphthalene by free and immobilized cells of Pseudomonas sp. strain NGK1

A Pseudomonas sp. strain NGK1 (NCIM 5120) capable of utilizing 2-methylnaphthalene (2-MN) was immobilized in various matrices namely, polyurethane foam (PUF), alginate, agar and polyvinyl alcohol (PVA) (1.5 × 10¹² c.f.u. g^–1 beads). The degradation rates of 25 and 50 mM 2-MN by freely suspended cells (2 × 10¹¹ c.f.u. ml^–1) and immobilized cells in batches, semi-continuous with shaken culture and continuous degradation in a packed-bed reactor were compared. The PUF-immobilized cells achieved higher degradation of 25 and 50 mM of 2-MN than freely suspended cells and the cells immobilized in alginate, agar or PVA. The PVA- and PUF-immobilized cells could be reused for more than 30 and 20 cycles respectively, without losing any degradation capacity. The effect of dilution rates on the rate of degradation of 25 and 50 mM 2-MN with freely suspended and immobilized cells were compared in the continuous system. Increase in dilution rate increased the degradation rate only up to 1 h^–1 in free cells with 25 mM 2-MN and no significant increase was observed with 50 mM 2-MN. With immobilized cells, the degradation rate increased with increase in dilution rate up to 1.5 h^–1 for 25 mM and 1 h^–1 for 50 mM 2-MN. These results revealed that the immobilized cell systems are more efficient than freely suspended cells for biodegradation of 2-MN.     

Horizontal reactor for the continuous production of ethanol by yeasts immobilized in pectin

Summary Yeast cells (Saccharomyces cerevisiae) were immobilized in pectin gel, incubated 12 h at 30°C and then used for the continuous production of ethanol employing a wedge-shaped horizontal reactor and sugar cane molasses as the carbon source. Under steady state conditions the mean residence time was 1.6 h and the volumetric productivity 40 g EtOH/hl. The gas evolved was easily released. Successive batch incubation in a synthetic medium substantially restored the fermentative capacity of the beads already used in the continuous assay.Departamento de Biotecnología y Bioingeniería, Centro de Investigación y de Estudios Avanzados del IPN, México D.F.Member of the Scientific Researcher's Career of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.     

Production of lysine by using immobilized livingCorynebacterium sp cells

Summary Lysine production by immobilizedCorynebacterium sp cells in alginate gel beads was investigated in flasks. ImmobilizedCorynebacterium sp cells exhibited a slightly greater lysine production than free cells and accumulated 60 g/l of L-lysine at maximum, when cultured for 120h in a medium containing 200g/l glucose as carbon source. Several factors, such as inoculum size, incubation time and alginate gel concentration were examined in order to improve lysine production by immobilized growing cells.     

Production of ethanol by immobilized Saccharomyces bayanus in an extractive fermentation system

An extractive fermentation system using immobilized yeast cells was developed to study the ethanol production at high sugar concentrations. Organic acids were used as extracting solvents of ethanol and their toxicity was tested in free and k-carrageenan entrapped cell preparations. Immobilization seems to protect cells against solvent toxicity, when long-chain organic acids, e.g., oleic acid, were used, probably due to steric and diffusional limitations, the free cells not being viable at high oleic acid concentrations. The entrapped cells also present a higher metabolic activity than their free counterparts at high glucose concentrations. A solution of 300 g/L of glucose was totally fermented by the immobilized yeast cells, which when free cannot normally convert more than 200 g/L. In situ recovery of ethanol by oleic acid in a batch immobilized cell system led to higher ethanol productivities and to the fermentation of 400 g/L, when an oleic acid/medium ratio of 5 was used.     

Production of pullulan from fuel ethanol byproducts byAureobasidium sp. strain NRRl Y-12,974

Summary Byproducts of fuel ethanol production from wet-milled corn, were tested as substrates for growth and pullulan production byAureobasidium sp. strain NRRL Y-12,974. The strain grew well on corn fiber and corn condensed distiller's solubles (CCDS), and fermented CCDS to pullulan. CCDS compared favorably with starch as a substrate for pullulan production.The use of brand or trade names may be necessary to report factually on available data. The USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable. All programs and services of the USDA are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap.     

Palatinose production by free and Ca-alginate gel immobilized cells of Erwinia sp.

Palatinose is a non-cariogenic disaccharide obtained from the enzymatic conversion of sucrose, used in food industries as a sugar substitute. Free and Ca-alginate immobilized cells of Erwinia sp. D12 were used to produce palatinose from sucrose. Palatinose production was studied in a repeated-batch process using different immobilized biocatalysts: whole cells, disrupted cells and glucosyltransferase. Successive batches were treated with the immobilized biocatalyst, but a decrease in palatinose production was observed. A continuous process using a packed-bed reactor was investigated, and found to produce 55–66% of palatinose during 17 days using immobilized cells treated with glutaraldehyde and a substrate flow speed of 0.56 ml min⁻¹. However, immobilized cells in a packed-bed reactor failed to maintain the palatinose production for a prolonged period. The free cells showed a high conversion rate using batch fermentation, obtaining a palatinose yield of 77%. The cells remained viable for 16 cycles with high palatinose yields (65–77%). Free Erwinia sp. D12 cells supported high production levels in repeated-batch operations, and the results showed the potential for repeated reuse.     

Production of xylanases by immobilized Aspergillus sp. using lignocellulosic waste

In shake flasks immobilized Aspergillus terreus and Aspergillus niger produced 29IU/ml, 26.7IU/ml xylanases at 10mg/ml, 14mg/ml wheat bran concentration after 48 and 60h of incubation at 37°C respectively. In repeated batch fermentation of immobilized Aspergillus sp. the same biocatalyst could be used for three successive cycles.     

Biodegradation of p-cresol by immobilized cells of Bacillus sp. strain PHN 1

The Bacillus sp. strain PHN 1 capable of degrading p-cresol was immobilized in various matrices namely, polyurethane foam (PUF), polyacrylamide, alginate and agar. The degradation rates of 20 and 40 mM p-cresol by the freely suspended cells and immobilized cells in batches and semi-continuous with shaken cultures were compared. The PUF-immobilized cells achieved higher degradation of 20 and 40 mM p-cresol than freely suspended cells and the cells immobilized in polyacrylamide, alginate and agar. The PUF- immobilized cells could be reused for more than 35 cycles, without losing any degradation capacity and showed more tolerance to pH and temperature changes than free cells. These results revealed that the immobilized cell systems are more efficient than freely suspended cells for degradation of p-cresol.     

Degradation of naphthalene by cells of Pseudomonas sp. strain NGK 1 immobilized in alginate, agar and polyacrylamide

A Pseudomonas sp. strain NGK 1 (NCIM 5120) was immobilized in various matrices, namely, alginate, agar (1.8 × 10¹¹ cfu g⁻¹ beads) and polyacrylamide (1.6 × 10¹¹ cfu g⁻¹ beads). The degradation of naphthalene was studied, by freely suspended cells (4 × 10¹⁰ cfu ml⁻¹) and immobilized cells in batches, with shaken culture and continuous degradation in a packed-bed reactor. Free cells brought about the complete degradation of 25 mmol naphthalene after 3 days of incubation, whereas, a maximum of 30 mmol naphthalene was degraded by the bacteria after 3–4 days of incubation with 50 mmol and 75 mmol naphthalene, and no further degradation was observed even after 15 days of incubation. Alginate-entrapped cells had degraded 25 mmol naphthalene after 3.5 days of incubation, whereas agar- and polyacrylamide-entrapped cells took 2.5 days; 50 mmol naphthalene was completely degraded by the immobilized cells after 6–7 days of incubation. Maximum amounts of 55 mmol, 70 mmol and 67 mmol naphthalene were degraded, from an initial 75 mmol naphthalene, by the alginate-, agar- and polyacrylamide-entrapped cells after 15 days of incubation. When the cell concentrations were doubled, 25 mmol and 50 mmol naphthalene were degraded after 2 and 5.5 days of incubation by the immobilized cells. Complete degradation of 75 mmol naphthalene occurred after 10 days incubation with agar- and polyacrylamide-entrapped␣cells, whereas only 60 mmol naphthalene was degraded by alginate-entrapped cells after 15 days of␣incubation. Further, with 25 mmol naphthalene, alginate-, agar- and polyacrylamide-entrapped cells (1.8 × 10¹¹ cfu g⁻¹ beads) could be reused 18, 12 and 23 times respectively. During continuous degradation in a packed-bed reactor, 80 mmol naphthalene 100 ml⁻¹ h⁻¹ was degraded by alginate- and polyacrylamide-entrapped cells whereas 80 mmol naphthalene 125 ml⁻¹␣h⁻¹ was degraded by agar-entrapped cells. Received: 21 October 1997 / Received revision: 15 January 1998 / Accepted: 18 January 1998     

Biodegradation of N-methylated carbamates by free and immobilized cells of newly isolated strain Enterobacter cloacae strain TA7

A bacterial strain (TA7) capable of consuming three N-methylated carbamates as sole nitrogen and carbon source was isolated and identified as “Enterobacter cloacae” on the basis of 16S rRNA, from carbamate contaminated agricultural soil by enrichment culture technique. The agar entrapment was used to immobilize the bacterial cells. Both the free as well as the immobilized cells were used to study the degradation of three carbamets viz. aldicarb, carbofuran, and carbaryl. The immobilized cells degraded all the three carbamates much faster than their free cell counterparts. The biodegradation kinetics of aldicarb, carbaryl, and carbofuran was studied using 50 ppm as initial concentration in the presence of free cells. The average values of K_s for aldicarb, carbofuran, and carbaryl were 22.6, 17.87, and 8.9 mg/L, respectively, whereas the values for µ_max were calculated as 1.35, 1.3, and 1.2 mg/l/h^?1. The results indicated that the bacterium has high affinity towards all the three carbamates. However, relatively higher affinity is for carbaryl, in comparison with carbofuran and aldicarb. Results indicate the potential of E. Cloacae TA7 to remediate N-methylated carbamates polluted water and soil.     

Production of ethanol by a stirred catalytic basket reactor with immobilized yeast cells

A stirred catalytic basket reactor with immobilized yeast cells was used for the batchwise production of ethanol. Fractional conversions up to 0.99 in 10 h were attained, depending on the agitation rates, initial glucose, and cell densities. The volumetric productivity of the reactor was considerably better than that of conventional stirred tank reactors. Productivities were strongly dependent on the stirred speed.     

根瘤菌BK-20固定化细胞生产L(+)-酒石酸

顺式环氧琥珀酸水解酶(CESH)是根瘤菌BK-20生产L(+)-酒石酸的关键酶。为提高其生产效率和生产稳定性,首先优化根瘤菌BK-20的产酶条件,然后利用固定化细胞连续生产L(+)-酒石酸。结果显示,优化后游离细胞酶活达(3 498.0±142.6)U/g,较优化前提高643%。固定化细胞酶活达(2 817.2±226.7)U/g,其最适包埋剂、菌体浓度和凝胶浓度分别为海藻酸钠,10%(W/V)和1.5%(W/V)。固定化细胞连续反应10批后,其形状和酶活均无明显改变,单批次转化率达98%以上,具有良好的生产稳定性。     

Production of rifamycin B and SV by free and immobilized cells of Amycolatopsis mediterranei

The effect of growth conditions (incubation time, inoculum size, initial pH value) and some nutrient concentrations on the growth and rifamycin B and SV production by free and immobilized cells of Amycolatopsis mediterranei CBS 42 575 was studied. In alginate beads, the immobilized cells behaved like the free cells, but a pronounced difference was observed in antibiotic production and cell growth. The rifamycin production by the immobilized cells was higher than that obtained by the free cells. The immobilized cells were also reused repeatedly for six batch cultivations with a fresh medium charged into flasks at the beginning of each batch. It was found that the immobilized cells were stable, and the rifamycin yield was almost constant during the first three batches and then decreased.     

Enhanced phenol degradation by immobilized Acinetobacter sp. strain AQ5NOL 1

A locally isolated Acinetobacter sp. Strain AQ5NOL 1 was encapsulated in gellan gum and its ability to degrade phenol was compared with the free cells. Optimal phenol degradation was achieved at gellan gum concentration of 0.75% (w/v), bead size of 3 mm diameter (estimated surface area of 28.26 mm²) and bead number of 300 per 100 ml medium. At phenol concentration of 100 mg l⁻¹, both free and immobilized bacteria exhibited similar rates of phenol degradation but at higher phenol concentrations, the immobilized bacteria exhibited a higher rate of degradation of phenol. The immobilized cells completely degrade phenol within 108, 216 and 240 h at 1,100, 1,500 and 1,900 mg l⁻¹ phenol, respectively, whereas free cells took 240 h to completely degrade phenol at 1,100 mg l⁻¹. However, the free cells were unable to completely degrade phenol at higher concentrations. Overall, the rates of phenol degradation by both immobilized and free bacteria decreased gradually as the phenol concentration was increased. The immobilized cells showed no loss in phenol degrading activity after being used repeatedly for 45 cycles of 18 h cycle. However, phenol degrading activity of the immobilized bacteria experienced 10 and 38% losses after the 46 and 47th cycles, respectively. The study has shown an increased efficiency of phenol degradation when the cells are encapsulated in gellan gum.