Hendrich Quitmann

Expression of enzymes for the usage in food and feed industry with Pichia pastoris.

The methylotrophic yeast Pichia pastoris is an established protein expression host for the production of industrial enzymes. This yeast can be grown to very high cell densities and produces high titers of recombinant protein, which can be expressed intercellularly or be secreted to the fermentation medium. P. pastoris offers some advantages over other established expression systems especially in protein maturation. In food and feed production many enzymatically catalyzed processes are reported and the demand for new enzymes grows continuously. For instance the unique catalytic properties of enzymes are used to improve resource efficiency, maintain quality, functionalize food, and to prevent off-flavors. This review aims to provide an overview on recent developments in heterologous production of enzymes with P. pastoris and their application within the food sector.

Kluyveromyces lactis: An emerging tool in biotechnology

Kluyveromyces lactis has emerged as one of the most important yeast species for research and industrial biotechnology. This Crabtree-negative species is suitable for the production of metabolites and heterologous proteins, and its ability to achieve high levels of protein secretion makes it an attractive alternative for industrial protein production. Since 1991, almost 100 recombinant proteins have been expressed in K. lactis, 20% of which have been produced in the last 2 years. This review provides an overview of the genetic modifications used to accomplish heterologous gene expression in K. lactis, as well as fermentation techniques, and recent examples of industrial proteins produced in this species.

Acidic Organic Compounds in Beverage, Food, and Feed Production

Organic acids and their derivatives are frequently used in beverage, food, and feed production. Acidic additives may act as buffers to regulate acidity, antioxidants, preservatives, flavor enhancers, and sequestrants. Beneficial effects on animal health and growth performance have been observed when using acidic substances as feed additives. Organic acids could be classified in groups according to their chemical structure. Each group of organic acids has its own specific properties and is used for different applications. Organic acids with low molecular weight (e.g. acetic acid, lactic acid, and citric acid), which are part of the primary metabolism, are often produced by fermentation. Others are produced more economically by chemical synthesis based on petrochemical raw materials on an industrial scale (e.g. formic acid, propionic and benzoic acid). Biotechnology-based production is of interest due to legislation, consumer demand for natural ingredients, and increasing environmental awareness. In the United States, for example, biocatalytically produced esters for food applications can be labeled as natural, whereas identical conventional acid catalyst-based molecules cannot. Natural esters command a price several times that of non-natural esters. Biotechnological routes need to be optimized regarding raw materials and yield, microorganisms, and recovery methods. New bioprocesses are being developed for organic acids, which are at this time commercially produced by chemical synthesis. Moreover, new organic acids that could be produced with biotechnological methods are under investigation for food applications.

Lactic Acid Production in a Membrane Bioreactor System with Thermophilic Bacillus coagulans: Fouling Analysis of the Used Ceramic Membranes

In lactic acid fermentation broth systems, membrane fouling is characterized as the crucial factor in limiting ceramic membrane life-time and efficiency. This study aimed to find the limiting factor of this process and seek an effective solution. By quantitative analysis using resistance-in-series model, the cake layer resistance is demonstrated to be the dominant factor in a steady state. A cake compressibility index was measured as high as 2.09. Within the low transmembrane pressure range, the cake resistance was manipulated through crossflow velocity regulation to achieve a better membrane performance. A new correlation between flux and cell density was also introduced.

Enzymatic production of fructooligosaccharides from inexpensive and abundant substrates using a membrane reactor system

ABSTRACT The concept of zero waste in the sugar industry has encouraged the development of technologies that promote utilization of by-products, including the enzymatic conversion of waste feed stocks into nutraceutical products. Here we investigated a membrane reactor for the production of fructooligosaccharides (FOS) with immobilized enzyme (Pectinex Ultra SP-L) system using pretreated molasses as substrate with cleaning efficiency and less fouling as performance tools. The resulting spectra showed a high FOS yield of 63% with 89% conversion from available sucrose. So, the enzymatic membrane reactor system with innovative continuous separation of enzyme was proved to fit for the production of FOS.

Lactic acid production in a membrane bioreactor system with thermophilic Bacillus coagulans: Online monitoring and process control using an optical sensor

ABSTRACT Membrane bioreactor systems can efficiently reduce product inhibition in lactic acid production processes, enhancing their productivity. Filtration parameters, e.g. crossflow velocity and transmembrane pressure, were controlled with varying biomass concentration, which was monitored using an optical sensor in real time. The filtration flux was successfully maintained as desired according to the control strategy. We also investigated the effect of feed concentration and dilution rate on process characteristics. The continuous fermentation remained stable for more than 80 h, achieving the highest productivity of 8.6 g·L–1·h–1 with a feed concentration of 70 g·L–1 and a dilution rate of 0.2 h–1.