Multistage Continuous Fermentation Research Articles

Production of butanol from biomass: recent advances and future prospects.

At present, diminishing oil resources and increasing environmental concerns have led to a shift toward the production of alternative biofuels. In the last few decades, butanol, as liquid biofuel, has received considerable research attention due to its advantages over ethanol. Several studies have focused on the production of butanol through the fermentation from raw renewable biomass, such as lignocellulosic materials. However, the low concentration and productivity of butanol production and the price of raw materials are limitations for butanol fermentation. Moreover, these limitations are the main causes of industrial decline in butanol production. This study reviews butanol fermentation, including the metabolism and characteristics of acetone-butanol-ethanol (ABE) producing clostridia. Furthermore, types of butanol production from biomass feedstock are detailed in this study. Specifically, this study introduces the recent progress on the efficient butanol production of "designed" and modified biomass. Additionally, the recent advances in the butanol fermentation process, such as multistage continuous fermentation, metabolic flow change of the electron carrier supplement, continuous fermentation with immobilization and recycling of cell, and the recent technical separation of the products from the fermentation broth, are described in this study.

Development of a multi-stage continuous fermentation strategy for docosahexaenoic acid production by Schizochytrium sp.

Docosahexaenoic acid (DHA) has wide-ranging benefits for normal development of the visual and nervous systems in infants. A sustainable source of DHA production through fermentation using Schizochytrium sp. has been developed. In this paper, we present the discovery of growth-uncoupled DHA production by Schizochytrium sp. and the development of corresponding kinetic models of fed-batch fermentations, which can be used to describe and predict the cell growth and substrate utilization as well as lipid and DHA production. Based on this kinetic model, a predictive model of multi-stage continuous fermentation process was established and used to analyze, optimize and design the process parameters. Optimal predicted processes of two-stage and three-stage continuous fermentation were developed and verified in lab-scale bioreactor based on the predicted process parameters. A successful three-stage continuous fermentation was achieved, which increased the lipid, DHA content and DHA productivity by 47.6, 64.3 and 97.1%, respectively, compared with two-stage continuous fermentation.

Characteristics of an Immobilized Yeast Cell System Using Very High Gravity for the Fermentation of Ethanol

The characteristics of ethanol production by immobilized yeast cells were investigated for both repeated batch fermentation and continuous fermentation. With an initial sugar concentration of 280 g/L during the repeated batch fermentation, more than 98% of total sugar was consumed in 65 h with an average ethanol concentration and ethanol yield of 130.12 g/L and 0.477 g ethanol/g consumed sugar, respectively. The immobilized yeast cell system was reliable for at least 10 batches and for a period of 28 days without accompanying the regeneration of Saccharomyces cerevisiae inside the carriers. The multistage continuous fermentation was carried out in a five-stage column bioreactor with a total working volume of 3.75 L. The bioreactor was operated for 26 days at a dilution rate of 0.015 h(-1). The ethanol concentration of the effluent reached 130.77 g/L ethanol while an average 8.18 g/L residual sugar remained. Due to the high osmotic pressure and toxic ethanol, considerable yeast cells died without regeneration, especially in the last two stages, which led to the breakdown of the whole system of multistage continuous fermentation.

A New Trend in Alcoholic Fermentation: Modelling and Optimal Steady State for a Continuous Cascade Ethanol Production

In order to control a pilot plant for multistage fermentation process production of ethanol, we have developed a simple model based only on sugar and alcohol concentrations. Identification reveals a good adequacy for various strains in batch and in continuous fermentation. We study an optimal design of a multistage continuous fermentation fed by the first stage as well for the vessel volumes as for the state variables in every vessel. Come results are given when the ethanol production speed is assumed to be a function of ethanol concentration, only. Then we treat the problem of going from initial to steady state using as feeding policy a fed batch in every vessel in order to maximize the conversion speed of sugar into alcohol.

Kinetics of polysaccharide B‐1459 fermentation

AbstractPolysaccharide gum was made by fermentation with Xanthomonas campestris NRRL B‐1459 in a medium of glucose, minerals, and distillers' solubles. The effect of distillers' solubles on growth rate can be described by the familiar saturation equation. Although a quasistoichiometric relationship was observed between nitrogen utilization and growth, total nitrogen supply was not growth limiting, nor was polymer formation growth associated. Cell growth primarily took place in the early part of the fermentation; polysaccharide biosynthesis occurred throughout the fermentation. Glucose was converted to polysaccharide at a fairly constant yield, which was 70–80% of glucose consumed, under optimum conditions. The kinetic patterns observed indicate that multistage continuous fermentation will be suitable for polysaccharide production.