Continuous ethanol production in the gas-lift tower fermenter

Summary A highly flocculent strain of Saccharomyces uvarum was used to convert glucose to ethanol and CO₂ in a single stage, continuous, gas-lift tower fermenter. Satisfactory operation was maintained in prolonged runs with yeast concentrations in excess of 100 g/L (d.w.) and hydraulic retention times less than 0.4 h. Maximum ethanol concentration and productivity were 88 g/L and 44.5 g/Lh respectively. Conversion efficiency was between 80 and 95% of theoretical.     

Continuous fermenter growth of a methionine-overproducing mutant of Candida utilis

Summary An ethionine resistant mutant of Candida utilis was found to maintain an expanded intracellular pool of free l-methionine in batch and continuous cultures. During glucose-limited growth in mineral salts medium in a continuous fermenter, the free l-methionine pool of the mutant was 40–80% higher than in batch cultures, and varied in the range of 25–30 moles/g dry cells (3.7–4.5 mg/g dry cells).     

Continuous Fermentation of Novobiocin

Continuous fermentation trials with Streptomyces niveus in a nine-stage fermentation system (7-liter reaction volume per stage) indicated that the cultures used gradually lost their ability to produce novobiocin when cultured over periods from 10 to 25 days. It was found that mycelial degeneration could be circumvented by operational means during continuous culture using the following technique: Two interchangeable 24-liter stages were installed at the front end of the nine-stage system and connected in parallel with the latter. Alternatingly one of these two tanks was then used as first stage of the continuous fermentation system. The holdup time in the first vessel was adjusted to limit cell growth chiefly to this stage so that most of the antibiotic production took place in subsequent stages. The first stages were switched at approximately weekly intervals. Each of the new tanks was prepared as a batch, inoculated with a high-producing cell population, and allowed to grow for 3 days before it was connected to the remaining system for continuous operation. Using this technique no evidence of culture degeneration was encountered in subsequent novobiocin production stages over a period of 33 days. In conventional runs without periodic replacement of the first stage, culture degeneration with the novobiocin fermentation occurred within a period of 10 to 25 days of continuous operation. This observation indicates that the described technique offers a solution to the problem of maintaining high steady-state titers in continuous novobiocin fermentations. Extension of this technique to other continuous fermentations where culture degeneration is a problem is indicated.     

高强度酒精连续发酵

从多株酒精酵母菌株中筛选出S.cerevisiaeKG作为酒精生产菌株。该菌株具有较好的酒精发酵活力和絮凝性。使用具有细胞循环的连续发酵双罐系统,酒精生产强度达到30.5（g／1.h）。根据该系统的动力学模型,讨论了获得高强度酒精连续发酵的途径。     

Effect of gas flow rate and oxygen concentration on the damping (filtering) action of fermenter head space

Summary The damping (filtering) action of head space and tubing of a fermenter was estimated. Dissolved oxygen tension in the culture and oxygen concentration in the outlet gas were measured during oscillatory condition and were used to estimate the damping action using fast Fourier transformation. The damping characteristics were found to be equal to a second order low pass filter with a cut off frequency of 1/500 Hz. The damping was found to be dependent on gas flow rate and oxygen concentration in the gas flow. Increasing the gas flow rate increased damping, however, increasing the oxygen content in the gas flow decreased damping. Data reconciliation of undamped oxygen concentrations in the outlet gas was performed using two different approaches.     

Continuous ethanol production in an immobilized whole cell fermenter using untreated sugar cane bagasse as carrier

Summary Saccharomyces cerevisiae was immobilised by adsorption to untreated sugar cane bagasse in a packed bed reactor. Complete conversion of glucose to ethanol was obtained at a dilution rate of 0.19 h⁻¹. Continuous ethanol production was maintained for up to 57 days. Reactor productivity increased with increasing packing density of the bagasse. Plugging of void spaces due to cell overgrowth led to channelling of the feed and decreased reactor productivity. Increasing the average column temperature alleviated plugging and restored column performance over a short period; however prolonged exposure to the high temperature resulted in decreased ethanol production rates. Bagasse has advantages as a support material for ethanol production from sugar cane or beet, including negligible cost, ready availability and the capacity to support a high yeast population.     

Theoretical Design of Continuous Antibiotic Fermentation Units

A graphic method of predicting antibiotic yields in continuous flow reactors is presented and discussed using the novobiocin fermentation as a model process. Extension to other antibiotic fermentations and steroid bioconversions is emphasized. In the case of the novobiocin fermentation it was concluded that a combination of one growth stage and one or two antibiotic production stages would be the most economic reactor system to conduct such a fermentation on a continuous basis.     

On-line thermal monitoring of aspartic acid separation in a high voidage ion-exchange column at high flow rate

A simple thermal monitoring technique has been successfully applied to an adsorption system using a novel ion exchanger with a large internal void volume (voidage) which can be operated at high superficial velocity (SV). Temperature changes resulting from heats of adsorption could be followed effectively using semi-conductor thermistor devices inserted into the resin through the column wall. Results show that, despite the high feed rates adopted, the thermal signals generated can be consistently related to the position of the breakthrough front within the bed.     

Low-pressure airlift fermenter for single cell protein production: II. Continuous culture of pichia yeast

Experiments using Pichia yeast grown on n-paraffins have been conducted in laboratory 10-L airlift fermenters and in a 640-L module of commercial scale. Results confirmed the design concept of combining oxygen transfer and fermenter cooling with low-pressure air. However, in the absence of mass transport constraints, the build up of toxic factors in the fermenter appeared to be a major variable limiting cell productivity. Foaming in the large fermenter also presented a serious problem, which must be solved before low-pressure airlift fermenters become practical.     

Continuous flow method in soil microbiology

Folia Microbiologica - A continuous flow method is described as applied to the investigation of microbiological processes taking place in soil samples. The principle of the method and its technical...     

Continuous high rate production of ethanol by Zymomonas mobilis in an attached film expanded bed fermentor

Summary Experiments were conducted with Zymomonas mobilis in an attached film expanded bed (AFEB) fermentor at different dilution rates, using a feed glucose concentration of 100 gm/l. Vermiculite was used as the bed material for attachment of the bacterial film. Ethanol volumetric productivities were maximum at a dilution rate of 3.6hr^-1. The productivities were 105 gm/l-hr and 210 gm/l-hr based on total fermentor volume and bed volume, respectively.     

Continuous flow method in soil microbiology

The decomposition of glycine in soil was studied by the continuous flow method. Glycine solution was added continuously to soil samples of different weights, i.e. soil columns of different heights. It was found that the extent of glycine mineralization was related to the weight of the soil. Glycine was nitrified most effectively in the soil sample weighing 30 g., in which 65.8% of the added (91.6% of the retained) glycine nitrogen was oxidized to nitrites and nitrates. No steady state was observed in the rate of nitrite and nitrate formation. The rate of nitrification rose at first, in relation to the weight of the soil, but fell after reaching the maximum. The factor limiting the rate of nitrification was the adsorption of ammonium nitrogen in the soil. By using soil samples of different weights and heights it was found possible to localize the process of ammonia release and the oxidation of ammonia and nitrites in the soil column and to influence the ratio of ammonification and nitrification or of the oxidation of ammonium ions and nitrites.     

Sulphite oxidation in the disc fermenter

Summary Sulphite oxidation in the disc fermenter showed an initial peak in the oxygen absorption rate followed eventually by a much lower constant final rate. The reaction was also found not to be diffusion controlled and therefore not suitable for measurement of true physical values of k_La.     

Continuous flow method in soil microbiology

The continuous flow method, applied to the study of microbiological processes in soil samples, was used to study the biological immobilization of mineral forms of nitrogen and phosphorus. By means of this method, physical-chemical adsorption of mineral elements was differentiated from biological immobilization over a given period. Biological immobilization of nitrogen and phosphorus was related to the metabolic activity of the soil microflora. It was found that the amount of biological immobilization of nitrogen and phosphorus was closely associated with glucose decomposition. A correlation was found between the immobilization of nitrate nitrogen and carbon dioxide evolution during glucose decomposition and the amount of glucose utilized. The ratio of the amount of glucose carbon assimilated by the soil microflora to the amount of nitrogen immobilized depended on the C∶N ratio in the added solution.     

Continuous flow method in soil microbiology

С применением непрерывно-проточного метода изучался метаболизм глюкозы в почве. Было установлено, что в применявшихся образцах почвы при данных условиях опыта от двух третей до трех четвертей прибавляемой глюкозы минерализуются и превращаются в CO₂. Ни степень минерализации глюкозы, прибавляемой к почве с начала опыта, ни скорость минерализации глюкозы в постоянном состоянии не зависят ни от концентрации глюкозы, ни от навески почвы, ни от присутствия минеральных форм азота и фосфора. Однако присутствие минеральных соединений азота и фосфора влияет на скорость минерализации гиюкозы в первой стадии процесса. Непрерывная подача глюкозы выразительно влияет на состав микробного сообщества почвы. При непрерывном протоке раствора одной только глюкозы число бактерий меняется лишь незначительно, но, с другой стороны, существенно повышается количество азотобактера. После предварительного насыщения почвы ионами фосфата аммония, или же при условии одновременной подачи минеральных питательных веществ и раствора глюкозы, наблюдается значительное повышение числа бактерий, тогда как азотобактер не размножается.     

Continuous Cellulosic Bioethanol Fermentation by Cyclic Fed-Batch Cocultivation

Cocultivation of cellulolytic and saccharolytic microbial populations is a promising strategy to improve bioethanol production from the fermentation of recalcitrant cellulosic materials. Earlier studies have demonstrated the effectiveness of cocultivation in enhancing ethanolic fermentation of cellulose in batch fermentation. To further enhance process efficiency, a semicontinuous cyclic fed-batch fermentor configuration was evaluated for its potential in enhancing the efficiency of cellulose fermentation using cocultivation. Cocultures of cellulolytic Clostridium thermocellum LQRI and saccharolytic Thermoanaerobacter pseudethanolicus strain X514 were tested in the semicontinuous fermentor as a model system. Initial cellulose concentration and pH were identified as the key process parameters controlling cellulose fermentation performance in the fixed-volume cyclic fed-batch coculture system. At an initial cellulose concentration of 40 g liter⁻¹, the concentration of ethanol produced with pH control was 4.5-fold higher than that without pH control. It was also found that efficient cellulosic bioethanol production by cocultivation was sustained in the semicontinuous configuration, with bioethanol production reaching 474 mM in 96 h with an initial cellulose concentration of 80 g liter⁻¹ and pH controlled at 6.5 to 6.8. These results suggested the advantages of the cyclic fed-batch process for cellulosic bioethanol fermentation by the cocultures.