Influence of probiotics on physico-chemical and organoleptic characteristics of sweet orange juice

Aim: The study was undertaken to evaluate the survival probiotic organisms and its influence on the physical, chemical, nutritional and sensory characteristics of sweet orange juice. Methodology: Two samples of probiotic juice were prepared with 10 percent innoculum containing LAB strains (Lactobacillus bulgaricus and Lactobacillus plantarum). Sample A (without encapsulated strains) and Sample-B (with encapsulated strains) were prepared and incubated for 10hrs at 35oC. After incubation, the physico-chemical analysis of both the samples were analyzed for TSS, pH, acidity, total sugars, reducing sugars and ascorbic acid content. Results: The results of TSS, pH, acidity, total sugars, reducing sugars and ascorbic acid content for sample –A and Sample –B were 11.4˚Brix, 3.51, 0.82 percent, 6.1 percent, 1.5 percent, 4.6 percent, 40mgml-1 and 11.6˚ Brix, 3.68, 0.77 percent, 6.4 percent, 1.7 percent, 4.9 percent, 40 mg ml-1, respectively. Sensory evaluation revealed that overall acceptance of probiotic juice containing encapsulated strains and free strains in the first week was 8.3 and 7.8, respectively. Even after 4 weeks of storage, the overall acceptance for juice with encapsulated strains was better than free strains with a score of 7.5 and 7.0 at the end of storage period. Interpretation: The sweet orange juice with encapsulated strains has high viable cell count (109cfu ml-1) even after 4 weeks of storage resulted in stable therapeutic probiotic sweet orange juice. It is further, suitable for commercial production of probiotic sweet orange juice with probiotic cultures.

Fitness effects of CTX-M-15-encoding IncF plasmids on their native Escherichia coli ST131 H30Rx hosts

Objectives: The objective of this study was to investigate effects of large CTX-M-15-encoding IncF plasmids on the fitness of their native E. coli ST131 H30Rx hosts in order to understand possible plasmid-host coevolution. Methods: We selected five E. coli ST131 H30Rx strains of diverse origin, each carrying a multireplicon IncF plasmid encoding the gene blaCTX-M-15. The plasmid was eliminated from each isolate by displacement using an incompatible plasmid vector pMDP5_cureEC958. Whole-genome sequencing (WGS) was performed to obtain complete chromosome and plasmid sequences of wild-type isolates and to detect chromosomal mutations in plasmid-free strains. Competition assays were conducted to determine the relative fitness of plasmid-free clones compared to the corresponding wild-type isolates. Results: We were able to successfully eliminate the IncF plasmids from all of the wild-type strains using the curing vector pMDP5_cureEC958. The chromosomes of plasmid-free clones contained zero to six point mutations. Plasmid-free strains of three isolates showed no significant difference in relative fitness compared to the corresponding plasmid-free strains. In the two remaining isolates, the plasmids produced a small but significant fitness cost. Conclusion: We conclude that IncF plasmids produce moderate fitness effects in their E. coli ST131 H30Rx hosts. This fitness compatibility is likely to promote the maintenance of antibiotic resistance in this worrisome E. coli lineage.

Chromosome Engineering To Generate Plasmid-Free Phenylalanine- and Tyrosine-Overproducing Escherichia coli Strains That Can Be Applied in the Generation of Aromatic-Compound-Producing Bacteria

ABSTRACT Many phenylalanine- and tyrosine-producing strains have used plasmid-based overexpression of pathway genes. The resulting strains achieved high titers and yields of phenylalanine and tyrosine. Chromosomally engineered, plasmid-free producers have shown lower titers and yields than plasmid-based strains, but the former are advantageous in terms of cultivation cost and public health/environmental risk. Therefore, we engineered here the Escherichia coli chromosome to create superior phenylalanine- and tyrosine-overproducing strains that did not depend on plasmid-based expression. Integration into the E. coli chromosome of two central metabolic pathway genes (ppsA and tktA) and eight shikimate pathway genes (aroA, aroB, aroC, aroD, aroE, aroGfbr, aroL, and pheAfbr), controlled by the T7lac promoter, resulted in excellent titers and yields of phenylalanine; the superscript “fbr” indicates that the enzyme encoded by the gene was feedback resistant. The generated strain could be changed to be a superior tyrosine-producing strain by replacing pheAfbr with tyrAfbr. A rational approach revealed that integration of seven genes (ppsA, tktA, aroA, aroB, aroC, aroGfbr, and pheAfbr) was necessary as the minimum gene set for high-yield phenylalanine production in E. coli MG1655 (tyrR, adhE, ldhA, pykF, pflDC, and ascF deletant). The phenylalanine- and tyrosine-producing strains were further applied to generate phenyllactic acid-, 4-hydroxyphenyllactic acid-, tyramine-, and tyrosol-producing strains; yield of these aromatic compounds increased proportionally to the increase in phenylalanine and tyrosine yields. IMPORTANCE Plasmid-free strains for aromatic compound production are desired in the aspect of industrial application. However, the yields of phenylalanine and tyrosine have been considerably lower in plasmid-free strains than in plasmid-based strains. The significance of this research is that we succeeded in generating superior plasmid-free phenylalanine- and tyrosine-producing strains by engineering the E. coli chromosome, which was comparable to that in plasmid-based strains. The generated strains have a potential to generate superior strains for the production of aromatic compounds. Actually, we demonstrated that four kinds of aromatic compounds could be produced from glucose with high yields (e.g., 0.28 g tyrosol/g glucose).

FITNESS BENEFITS TO BACTERIA OF CARRYING PROPHAGES AND PROPHAGE-ENCODED ANTIBIOTIC-RESISTANCE GENES PEAK IN DIFFERENT ENVIRONMENTS

Bacteria can acquire antibiotic resistance genes (ARGs) via prophages, phage genomes integrated into bacterial chromosomes. Such prophages may influence bacterial fitness via increased antibiotic resistance, protection from further phage infection, or by switching to a lytic lifecycle that releases free phages which can infect phage-susceptible competitors. We expect these effects to depend on environmental conditions because of, for example, environment-dependent induction of the lytic lifecycle. However, our understanding of how costs and benefits of prophage-encoded ARGs vary across environments remains limited. Here, by studying prophages with and without ARGs in Escherichia coli, we distinguished between effects of prophages alone and ARGs they carry. In competition with prophage-free strains, fitness benefits from prophages and ARGs peaked in different environments. Prophage carriage was most beneficial in conditions where induction of the lytic lifecycle was common, whereas ARGs were more beneficial in the presence of antibiotics and when prophage induction was lower. Acquisition of prophage-encoded ARGs by competing phage-susceptible strains was most common when prophage induction, and therefore the amount of free phages, was high. Thus, selection on prophages and ARGs varies independently across environments, which is important for predicting the spread of mobile/integrating genetic elements and their role in antibiotic resistance evolution.

Enhancement the Enzymatic Activity of Phenol-Degrading Microbes Immobilized on Agricultural Residues during the Biodegradation of Phenol in Petrochemical Wastewater

In this study, we illustrated enhanced biodegradation enzyme activity and the strains growth using the plants residues as carriers during the biodegradation of phenol in petrochemical wastewater. The three phenol-degrading strains named as A1, A2 and A3 were selected for an immobilized microorganism technique. A1, A2 and A3 were identified asPenicilliumoxalicum,Aspergillussp. andSphingobacteriumsp. using detailed morphological, biochemical and molecular characterization. The growth and degradation rate of phenol in wastewater by strains A1, A2 and A3 pre-grown in the agricultural residues (peanut shell) were higher than the free strains. Compared with the free strains,the enzyme activity of strains A1,A2 and A3, using the residues for pre-grown, increased 29.01 U/L, 30.30 U/L and 38.07 U/L, respectively. Hence, the immobilized microorganism technique is conducive to the phenol degradation.

Stress-Free Strains in Martensitic Microstructures

The peculiar properties of shape-memory alloys are the result of a solid/solid phase transformation between different crystallographic structures (austenite and martensite). This paper is concerned with the theoretical prediction of the set of strains that minimize the effective (or macroscopic) energy. Those strains, classically refered to as recoverable strains, play a central role in shape memory effect displayed by alloys such as NiTi or CuAlNi. They correspond to macroscopic strains that can be achieved in stress-free states. Adopting the framework of nonlinear elasticity, the theoretical prediction of stress-free strains amounts to find the austenite/martensite microstructures which minimize the global energy. Closed-form solutions to that problem have been obtained only in few special cases. This paper aims at complementing existing results on that problem, essentially by deriving bounds on the set of stress-free strains.

Comparing the efficacy of plasmid curing agents in Lactobacillus acidophilus

This study was mainly focused on plasmid profiling and plasmid characterisation of Lactobacillus acidophilus isolated from molasses. The secondary objective was to observe the efficacy of the plasmid curing agents acriflavine, ethidium bromide, novobiocin and SDS on L. acidophilus. Plasmid-free strains and cured derivatives harbouring only a single plasmid (6.2 kbp) were also obtained. Treatment of L. acidophilus with novobiocin at concentrations of 2.4 µg/ml could produce a large number of chloramphenicol- variants at a very high frequency (4.6%). These curing data confirmed that novobiocin acts as an effective curing agent for L. acidophilus.