The ability of probiotic bacteria to adhere to the intestinal epithelium play an important role in colonization of the gastrointestinal tract, preventing their elimination by peristalsis and providing a competitive advantage in this ecosystem. To identify bacterial traits related to adhesion the probiotic strain L. acidophilus M92 was examined for autoaggregation ability and cell surface hydrophobicity L. acidophilus M92 exhibits a strong autoaggregation phenotype and also coaggregation with some pathogen microorganisms that may form a barrier that prevents their colonization. The examined probiotic strain manifests a good degree of hydrophobicity determined by microbial adhesion to hydrocarbons. Aggregation and hydrophobicity were abolished upon exposure of the cells to pronase, which suggests the possible role of cell surface layer (S-layer) proteins, approximated at 45 kDa, in a L. acidophilus M92. The relationship between autoaggregation and adhesion ability to intestinal tissue was investigated by observing the adhesivity of L. acidophilus M92 to porcine ileal epithelial cells. Removal of the S-layer proteins by extraction with 5 M LiCl reduced autaggregation and in vitro adhesion of this strain.

Adhesion and aggregation ability of probiotic strain Lactobacillus acidophilus M92

Bioethanol is one of the most promising and eco-friendly alternatives to fossil fuels, which is produced from renewable sources. Although almost all the current fuel ethanol is generated from edible sources (sugars and starch), lignocellulosic biomass (LCB) has drawn much attention in recent times. However, the conversion efficiency as well as ethanol yield of the biomass differs greatly with respect to the source and nature of LCB, primarily due to the variation in lignocellulosic content. Two major polysaccharides in LCB, namely, cellulose and hemicellulose firmly link to lignin and form a complex lignocellulosic network, which is highly robust and recalcitrant to depolymerization. For this reason, generation of ethanol from LCB requires a complicated conversion process that has made it commercially non-competitive. As attempts to exploit LCBs into commercial ethanol production, recent research efforts have been devoted to the techno-economic improvements of the overall conversion process, in addition to screen out promising feedstocks. This review paper presents an overview on the diversity of biomass, technological approaches and microbial contribution to the conversion of LCB into ethanol.

Fuel ethanol production from lignocellulosic biomass: an overview on feedstocks and technological approaches.

Digestion of food depends on three main factors: (i) the ingested food and the extent to which the food is susceptible to the effects of digestive enzymes, (ii) the activity of the digestive enzymes and (iii) the length of time the food is exposed to the action of the digestive enzymes. Each of these factors is affected by a multitude of secondary factors. The present review highlights the experimental results on the secondary factor, enzymatic activity and possible contribution of the fish gut microbiota in nutrition. It has been suggested that fish gut microbiota might have positive effects to the digestive processes of fish, and these studies have isolated and identified the enzyme-producing microbiota. In addition to Bacillus genera, Enterobacteriaceae and Acinetobacter, Aeromonas, Flavobacterium, Photobacterium, Pseudomonas, Vibrio, Microbacterium, Micrococcus, Staphylococcus, unidentified anaerobes and yeast are also suggested to be possible contributors. However, in contrast to endothermic animals, it is difficult to conclude the exact contribution of the gastrointestinal microbiota because of the complexity and variable ecology of the digestive tract of different fish species, the presence of stomach and pyloric caeca and the relative intestinal length. The present review will critically evaluate the results to establish whether or not intestinal microbiota do contribute to fish nutrition.

Enzyme‐producing bacteria isolated from fish gut: a review

Bioethanol is an attractive biofuel having potential for energy security and environmental safety over fossil fuels. To date, numerous biomass resources have been investigated for bioethanol production, which can broadly be classified into sugars, starch and lignocellulosic biomass. However, conversion of biomass into ethanol varies considerably depending on the nature of feedstock, primarily due to the variation in biochemical composition, and so, only a few feedstocks have been exploited commercially. In recent years, the conversion process of biomass has been improved significantly, even though most of these achievements are yet to be implemented in commercial facility. All the major steps in a typical conversion process, particularly fermentation of sugars that is the common step for all biomass, are greatly influenced by microorganisms. A traditional yeast, Saccharomyces cerevisiae, and a bacterial species, Zymomonas mobilis, are widely used in the ethanol fermentation technology. Many factors affect ethanol production process, and the final yield is directly associated with the optimum conditions of these attributes. This review paper presents an overview on the first and second generation bioethanol production with a particular attention to the potential of various biomass sources, technological approaches, role of microorganisms and factors affecting ethanol production process.

Bioethanol production from renewable sources: Current perspectives and technological progress

Lignocellulosic materials are among the most promising alternative energy resources that can be utilized to produce cellulosic ethanol. However, the physical and chemical structure of lignocellulosic materials forms strong native recalcitrance and results in relatively low yield of ethanol from raw lignocellulosic materials. An appropriate pretreatment method is required to overcome this recalcitrance. For decades various pretreatment processes have been developed to improve the digestibility of lignocellulosic biomass. Each pretreatment process has a different specificity on altering the physical and chemical structure of lignocellulosic materials. In this paper, the chemical structure of lignocellulosic biomass and factors likely affect the digestibility of lignocellulosic materials are discussed, and then an overview about the most important pretreatment processes available are provided. In particular, the combined pretreatment strategies are reviewed for improving the enzymatic hydrolysis of lignocellulose and realizing the comprehensive utilization of lignocellulosic materials.

The role of pretreatment in improving the enzymatic hydrolysis

Application of ionic liquid and alkali pretreatment for enhancing saccharification of sunflower stalk biomass for potential biofuel-ethanol production.

Streptomyces sp. 7b showed highest xylanase activity among 41 bacterial isolates screened under submerged fermentation. The organism grew over broad pH (5-11) and temperatures range (25-55 degrees C) and displayed maximum xylanase production on wheat bran (1230 U/g) under solid-state fermentation. Xylanase production was enhanced substantially (76%-77%) by inclusion of trypton (2180 U/g) or beef extract (2170 U/g) and moderately (36%-46%) by yeast extract (1800 U/g) or soybean meal (1670 U/g). Inclusion of readily utilizable sugars such as glucose, maltose, fructose, lactose or xylose in the substrate repressed the xylanase production. The optimum initial pH of the medium for maximum enzyme production was 7 to 8; however, appreciable level of activity was obtained at pH 6 (1,680 U/g) and 9 (1,900 U/g). Most appropriate solid to liquid ratio for maximum xylanase production in solid-state fermentation was found to be 1:2.5. The organism produced a single xylanase of molecular weight of approximately 30 kDa as analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis after purification with ammonium sulfate precipitation, and carboxy methyl sephadex chromatography. The enzyme was purified to the extent of 5.68-fold by salt precipitation and ion-exchange chromatography. Optimum temperature and pH for maximum xylanase activity were 50 degrees C and 6, respectively.

Production of Xylanase From an Alkalitolerant Streptomyces sp. 7b Under Solid-State Fermentation, Its Purification, and Characterization

Bacterial isolate Bacillus licheniformis P11(C) efficiently utilized agricultural residues as carbon and nitrogen sources to generate substantial amount of xylanase which exhibited activity and stability over broad pH range (5–11) and over elevated temperatures (40–100 °C), and even in presence of potential inhibitors (triton, SDS, EDTA). Purification of xylanase (4.24-fold) by ammonium sulphate precipitation and DEAE-sepharose chromatography, and analysis by SDS-PAGE and zymography showed that B. licheniformis P11(C) produced two xylanases (17.5 and 23 kDa). Furthermore, xylanase displayed exciting potential for application in fruit juice processing and bakery processes; enzyme was found to be effective in getting enhanced sugar extraction from fruit juices, clarification of fruit juices, and substantial dough-raising in bakery.

Production and characterization of xylanase from Bacillus licheniformis P11(C) with potential for fruit juice and bakery industry

Ultrasound and surfactant assisted ionic liquid pretreatment of sugarcane bagasse for enhancing saccharification using enzymes from an ionic liquid tolerant Aspergillus assiutensis VS34.

Cellulases to be employed for lignocellulose bioconversion for biofuel (ethanol) industry or for production of other specialty chemicals must be extremely robust to withstand harsh industrial conditions like extremes of temperature, pH, presence of inhibitory agents etc. In the present study the Bacillus strain M-9 isolated from decomposing rice bran produced significant amount of endoglucanase after 72 h of fermentation. Endoglucanase was partially purified by ammonium sulphate precipitation (20-50% saturation) and characterized for few properties. The endoglucanase showed activity over broad range of temperatures (30-100 o C) with maximum activity at 60 o C. The enzyme retained 50 and 39% of the maximum activity at 90 and 100 o C, respectively. The enzyme was thoroughly stable at 50-70 o C for 30 min-1 h. The endoglucanase showed activity over a wide range of pH (3-10) with maximum activity at pH 5. Detergents (SDS, Tween 80), metal ions (Zn 2+ , Pb 2+ ) and EDTA caused little to moderate reduction in enzyme activity. The endoglucanase was purified to the extent of 9.06 folds by salt precipitation and DEAE-cellulose chromatography. Endoglucanase showed molecular weight of approximately 54 kDa as examined by SDS-PAGE. High thermostability and acid/alkalistability of the endoglucanase reflect potential commercial significance of the enzyme.

http://nopr.niscair.res.in/bitstream/123456789/6161/1/IJCT%2016%285%29%20382-387.pdf

Bijender Kumar Bajaj

Papers

Application of ionic liquid and alkali pretreatment for enhancing saccharification of sunflower stalk biomass for potential biofuel-ethanol production.

Production of Xylanase From an Alkalitolerant Streptomyces sp. 7b Under Solid-State Fermentation, Its Purification, and Characterization

Production and characterization of xylanase from Bacillus licheniformis P11(C) with potential for fruit juice and bakery industry

Ultrasound and surfactant assisted ionic liquid pretreatment of sugarcane bagasse for enhancing saccharification using enzymes from an ionic liquid tolerant Aspergillus assiutensis VS34.

Partial purification and characterization of a highly thermostable and pH stable endoglucanase from a newly isolated Bacillus strain M-9