Sauerkraut fermentation : New fermentation vat

Summary A new sauerkraut fermentation vat with external recycling of brine is described. This system allows the control of fermentation, improves the homogeneity of final product and accelerates theacidification by the usual lactic-acid bacteria.     

D-xylulose fermentation in yeasts

Summary With pure D-xylulose as substrate, Schizosaccharomyces pombe produced ethanol in good yield with low quantities of polyols as by-products. Saccharomyces cerevisiae was found to be a good alcohol producer in glucose but not as good in D-xylulose. Other yeast cultures converted D-xylulose to xylitol, or D-arabitol or both, with lower ethanol yield.     

Mass transfer in fermentation

An essential consideration in the design and operation of commercial fermenters is to ensure adequate mass transfer. The complex composition of fermentation liquids makes it difficult to predict accurately the mass transfer characteristics in large vessels. Here various aspects of mass transfer are discussed and their relationships examined. Strategies for predicting the most important type of mass transfer — between gases and liquids — in large scale fermentations are presented.     

Breadfruit fermentation in micronesia

Throughout Oceania, pit fermentation of starchy crops was used as means of ensuring a predictable food supply despite the vagaries of drought, cyclonic storms, and warfare. During a 6-mo period, fermentation techniques for breadfruit (Artocarpus altilis) were studied in Micronesia in the islands comprising Majuro, Guam, Belau, Yap, and Ponape. Fermentation techniques were found to vary throughout Micronensia but as a whole to differ significantly from techniques used in Polynesia. We believe the benefits of such food preservation technologies to be significant in facilitating colonization of temporally marginal island environments.     

Recycle in fermentation processes

Until recently, the recycle of the solid (microbial), liquid, or gaseous phases in microbiological processes has only been practiced rarely, with the notable exception of activated sludge processes for wastewater treatment, where recycling of a large fraction of the microbial phase is essential for process stability and performance. During the last decade, the economic impact of a number of politically motivated changes with respect to energy and feedstock costs and availability, and legislation directed towards markedly higher levels of environmental protection have encouraged the evaluation and subsequent development of recycle technology in the fermentation industry. Many of the developments have occurred in isolation and some have failed to result in either an improvement in process economics or any reduction in the quantity of pollutants discharged. This article seeks to review the present diversity of approaches to recycle technology in fermentation processes in order to provide a sensible basis for future developments.     

Rice fermentation in ecuador

Fermented rice, or “Sierra rice”, of Ecuador, is distributed and consumed exclusively in the Andean Sierra. Fermenting precooks the rice, thus reducing the cooking time in the Andean Highlands. “Sierra rice” is the only type used in preparation of “dry rice”, which is considered indispensable to all meals.     

Comparative study of protease production in solid substrate fermentation versus submerged fermentation

Attempts have been made to compare solid substrate fermentation (SSF) with submerged fermentation for the production of proteases by Bacillus amyloliquefaciens. In submerged fermentation it produced 800,000 units of enzyme under optimal conditions in a 20-litre fermentor whereas in solid substrate, it produced 250,000 units/g. Owing to the simplicity and easiness of operation of SSF and for applications like unhairing, biodetergents and bating the former would be advantageous for the production of proteases.     

Kocho fermentation

Kocho, an acidic starchy food, is prepared by fermenting a mixture of the scraping of the trunk and pulverized stem and corm of ensette ( Ensette ventricosum). Leuconostoc mesenteroides is responsible for initiating the fermentation. Because of the activities of this species and, to some extent, of Streptococcus faecalis , the pH of the fermenting kocho was reduced from 6˙5 to 5˙6. These organisms were then succeeded by the homofermentative bacteria Lactobacillus coryneformis subsp. coryne-formis and Lact. plantarum . Through the activities of the Lactobacillus species, the pH was further reduced to 4˙2. Pediococcus cerevisiae , although present in kocho, did not achieve prominence because of the relatively low fermentation temperature (14°-18°C). Spore-formers were present in fairly high numbers during the first 15 d of fermentation. It was suspected that the butyrous odour which was detected during the first 2 weeks in fermenting kocho might be due to the activities of certain clostridial species. Yeasts were also present in fairly high numbers.     

Miso fermentation

Miso is a fermented food widely consumed in the Orient and is prepared from mold rice, soybeans and salt. About 13 million bushels of soybeans are made into miso each year, the annualproduction amounting to 974,000 metric tons.     

Solid-state fermentation

Solid-state fermentation has emerged as a potential technology for the production of microbial products such as feed, fuel, food, industrial chemicals and pharmaceutical products. Its application in bioprocesses such as bioleaching, biobeneficiation, bioremediation, biopulping, etc. has offered several advantages. Utilisation of agro-industrial residues as substrates in SSF processes provides an alternative avenue and value-addition to these otherwise under- or non-utilised residues. Today with better understanding of biochemical engineering aspects, particularly on mathematical modelling and design of bioreactors (fermenters), it is possible to scale up SSF processes and some designs have been developed for commercialisation. It is hoped that with continuity in current trends, SSF technology would be well developed at par with submerged fermentation technology in times to come.     

Inducing malolactic fermentation in wines

Malolactic fermentation (MLF) in wine can be accomplished by relying on the natural microflora or by inducing through inoculation of a specific strain(s) of malolactic bacteria, primarily strains of Leuconostoc oenos. Problems with inducing MLF include intrinsic factors of the grape must such as pH, presence of sulfur dioxide, and ethanol in addition to antagonism of malolactic bacteria by wine yeast. Current methods and new technology to improve the predictability of MLF are discussed.     

Continuous fermentation in slant tubes

Continuous, steady-state grape-juice fermentation, carried out in experimental slant-tube fermentors, was characterized by complete fermentation, even at fast pumping rates, because efficient cell retention, as well as rapid yeast growth, quickly built cell density up to the limit permitted by the juice supply rate. Essentially complete fermentation was easily achieved with a juice residence time of 3.1 hr, compared to about 120 hr in normal batch fermentation. Successful continuous fermentation required constancy of gas and liquid flow through the tubes, placing some restrictions on choice of tube configurations. The validity of design equations, developed previously from a settling model, was tested, and some practical aspects of their application to fermentor design and operation were demonstrated.     

pH modelling in fermentation broths

A model of broth pH has been established based upon the mineral requirements of the microorganism, the substrate consumption and the metabolites production. It has been tested on acetic acid, citric acid and yeast fermentations. It has then been used to predict the mineral composition of the feed for fedbatch growth of Saccharomyces cerevisiae.     

Oxygen requirement in pullulan fermentation

Summary Oxygen was essential for the biosynthesis of pullulan by Aureobasidium pullulans. In a growth medium, pullulan yield and synthesis rate were proportional to the oxygen availability. However, under controlled oxygen environment in a non-growth medium, the synthesis rate and the yield of pullulan were inversely proportional to the oxygen tension. A relationship between melanin production and oxygen transfer conditions was also observed. The elapsed time prior to the appearance of the pigment was dependent upon the degree of oxygen availability.     

Aerobic fermentation in tobacco pollen

We characterized the genes coding for the two dedicated enzymes of ethanolic fermentation, alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC), and show that they are functional in pollen. Two PDC-encoding genes were isolated, which displayed reciprocal regulation: PDC1 was anaerobically induced in leaves, whereas PDC2 mRNA was absent in leaves, but constitutively present in pollen. A flux through the ethanolic fermentation pathway could be measured in pollen under all tested environmental and developmental conditions. Surprisingly, the major factor influencing the rate of ethanol production was not oxygen availability, but the composition of the incubation medium. Under optimal conditions for pollen tube growth, approximately two-thirds of the carbon consumed was fermented, and ethanol accumulated into the surrounding medium to a concentration exceeding 100 mM.