The Use of Biopreservatives in the Control of Bacterial Contaminants of Sugarcane Alcohol Fermentation

ABSTRACT: Efficacy and safety of biopreservatives were studied for microbiological control of alcohol fermentation. Minimum inhibitory concentrations of nisin and lysozyme, and combinations with EDTA and Tween 20, were determined for Lactobacillus plantarum, L. fermentum , and L. confusus. The highest MIC value for nisin was 9.0 ppm for L. fermentum. Lysozyme was efficient against L. plantarum (700 ppm). A 2⁴ factorial design was used to study the effect of biopreservatives and potentiators on the growth kinetics of Lactobacillus fermentum. The combination of 8.6 ppm of nisin plus 0.1% of Tween 20 delayed the lag phase by 12 h. The biopreservatives did not affect the fermentation kinetics of Saccharomyces cerevisiae.     

Cassava retting: Optimisation of a traditional fermentation by an experimental research methodology

Retting, a spontaneous and traditional fermentation of cassava roots in Central Africa, was optimised in terms of time and the quality of the end-product. Optimal conditions were achieved by using an experimental research methodology. Temperature is the most influential factor, with an optimum of 34°C for quicker retting. The roots should be peeled and soaked in water immediately after harvesting to increase the quality of cassava foods. Inoculation of water with juice from a prior retting helps in cassava detoxification but has no influence on the time or the quality of foo-foo. Foo-foo samples had the most favourable organoleptic quality when an incubation temperature of between 28 and 37°C was used. Using optimal conditions, retting time was reduced 3-fold, and foo-foo of high and constant quality could be processed.     

Astaxanthin Extraction From Shrimp Waste by Lactic Fermentation and Enzymatic Hydrolysis of the Carotenoprotein Complex

ABSTRACT: Natural carotenoids are an alternative to synthetic orange-red pigments. They are present in crustaceans as a protein-pigment complex. In order to extract this highly unstable pigment, crustacean waste must be stabilized; lactic fermentation is a simple and environmentally friendly method to achieve this goal. Shrimp wastes were inoculated with Lactobacillus bacterial cultures. Carotenoids were then extracted with an organic solvent system. Protein-pigment splitting was carried out using a mixture of 4 commercial enzymes; and the protein was separated from the pigment by ultrafiltration. Electrophoretograms showed that the pigment was attached to a 265-kDa protein. Splitting the protein-pigment complex allows studies on pigment absorption, stability and application.     

Mashing of rice with barley malt under non-conventional process conditions for use in food processes

Non-conventional mashing conditions are relevant in the development of a lactic acid-fermented soymilk beverage where mashed rice is the source of carbohydrates for the fermentation and sweetness of the beverage. Advantages in the process layout could be achieved by mashing at higher pH and lower malt concentrations than normally used in the brewing industry. the work reported here assessed the consequences of mashing under non-conventional conditions. Malt concentration in the cereal part was varied from 25% to 70% (w/w), pH was varied within 5.3 to 7.1, and prolongation of the holding times at 50°C and 62°C was investigated. Regression equations have been established for predicting yields of soluble protein, low molecular weight sugars and total fermentability as functions of pH and malt concentration. the results showed that the maltose yield was constant while glucose, maltotriose and total fermentable sugar yields decreased slightly with increasing pH and decreasing malt concentration. Prolonged mash holding times at 50°C and 62°C gave minor increases in protein yields only. It is concluded that it is quite acceptable to use non-conventional mashing conditions when a mashing step is integrated in other food processes.     

Volatile constituents of palm wine and palm sap

Palm wine and pasteurised palm sap volatiles were collected, concentrated on a Tenax GC and analysed by gas chromatography and gas chromatography-mass spectrometry. Eighty-two components were identified: 47 esters, 9 alcohols, 5 acids, 6 carbonyls, 2 acetals, 4 terpenes and 9 hydrocarbons. These had all been found previously in conventional wines. Odour evaluation of the separated palm wine components as they eluted suggested that no one compound is responsible for the characteristic palm wine odour. The acetates of higher alcohols and the ethyl esters of straight-chain aliphatic C₆-C₁₀ acids seemed to be important and may play a big role in imparting the fruity nuances of characteristic palm wine odour. Their association with alcohols seemed also to be necessary for the expression of typical palm wine odour. The qualitative difference between palm sap aroma and palm wine aroma appeared to be due mainly to the presence of these esters and alcohols in palm wine and their apparent absence from palm sap, as well as to the presence of some low-boiling esters and alcohols in palm sap and their apparent absence from palm wine.     

Effects of temperature, ammonium and glucose concentrations on yeast growth in a model wine system

In enology, alcoholic fermentation is a complex process involving several mechanisms. Slow and incomplete alcoholic fermentation is a chronic problem for the wine industry and factors leading to sluggish and stuck fermentations have been extensively studied and reviewed. The most studied cause of sluggish and stuck fermentation is the nitrogen content limitation. Nevertheless, other factors, such as temperature of fermentation and sugar concentration can affect the growth of yeasts. In this study we modelled the yeast growth‐cycle in wine model system as a function of temperature, sugar and ammonium concentrations; the individual effects and the interaction of these factors were analysed by means of a quadratic response surface methodology. Cell concentrations and weight loss were monitored in the whole wine fermentation process. The results of central composite design show that lower is the availability of nitrogen, higher is the cell growth rate; moreover, initial nitrogen concentration also influences survival time of Saccharomyces cerevisiae.     

Bioprocess applications of model-based estimation techniques

The last decade has seen the development of a number of approaches for estimating those variables which are difficult to measure on-line in industrial process situations. Whilst a range of techniques is available, a common element is the use of process knowledge in the form of a system model. In the case of bioprocess systems, although a large range of models has been presented in the literature, their use in estimation schemes on an industrial scale has been limited. A number of reasons can be identified for their low level of utilisation. Of particular significance is the uncertainty which exists in quantifying system performance and the process-model mismatch which inevitably results. The level of ‘pre-defined model’ uncertainty, together with the knowledge gained during the course of the fermentation, serves to dictate estimator structure. The paper considers a range of estimation strategies and contrasts, through industrial applications, their performance characteristics and utility.     

IMP2, a nuclear gene controlling the mitochondrial dependence of galactose, maltose and raffinose utilization in Saccharomyces cerevisiae.

The IMP2 gene of Saccharomyces cerevisiae is involved in the nucleo-mitochondrial control of maltose, galactose and raffinose utilization as shown by the inability of imp2 mutants to grow on these carbon sources in respiratory-deficient conditions or in the presence of ethidium bromide and erythromycin. The negative phenotype cannot be scored in the presence of inhibitors of respiration and oxidative phosphorylation, indicating that the role of the mitochondria in the utilization of the above-mentioned carbon sources in imp2 mutants is not at the energetical level. Mutations in the IMP2 gene also confer many phenotypic alterations in respiratory-sufficient conditions, e.g. leaky phenotype on oxidizable carbon sources, sensitivity to heat shock and sporulation deficiency. The IMP2 gene has been cloned, sequenced and disrupted. The phenotype of null imp2 mutants is indistinguishable from that of the originally isolated mutant.     

抗生素生产过程补料时机的Fuzzy识别与预报

本文就抗生素发酵生产过程,提出了一种补料时机的Fuzzy识别、预报的建模方法,并根据20m~3发酵罐工业数据的分析,选取了以总糖、总糖变化率、氨基氮和氨基氮变化率四个主要参数作为输入集因素,运用本文提出的方法,建立了一个实际的抗生素发酵生产过程补料时机的 Fuzzy 识别、预报模型。经现场调试效果良好,与富有经验的行家相比,准确率达90%以上。     

生态环保复合药肥的研制与生产

选用多种有机物为原料,经酵素发酵或活化处理,配入以腐植酸为载体的综合有益生物菌剂,再添加适量含氮、磷、钾、钙、镁、硫、硅的肥料及微量元素、稀土等,生产生态环保复合药肥。介绍其工艺、产品质量及特点。该药肥对生态环保和农业增产效果显著。