Aromatic Amino Acid Catabolism by \u3cem\u3eLactobacillus spp\u3c/em\u3e.: Biochemistry and Contribution to Cheese Flavor Development

Amino acids derived from the degradation of casein in cheese serve as precursors for the generation of desirable and undesirable flavor compounds. Microbial degradation of aromatic amino acids is associated with the formation of aroma compounds that impart putrid-fecal, barny-utensil, and floral off-flavors in cheese, but pathways for their production had not been established. This study investigated Tyr and Phe catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts under simulated Cheddar cheese-ripening conditions (pH 5.2, 4% NaCl, 15°C, no sugar). Enzyme assays of cell-free extracts and micellar electrokinetic capillary chromatography of supernatants indicated that L. casei and L. helveticus strains catabolize Tyr and Phe by successive transamination and dehydrogenation reactions. Major products of Tyr and Phe catabolism included off-flavor compounds formed by chemical degradation of the α-keto acids, produced by transamination, and aromatic α-hydroxy acids derived from α-keto acids by α-hydroxy acid dehydrogenases. Action of Lacrococcus lactis aminotransferase enzymes on Trp, Tyr, and Phe also leads to the formation of α-keto acids, but unlike lactobacilli, the former bacteria do not express dehydrogenase activity under cheese-like conditions (pH 5.2, 4% NaCl, 15°C, no sugar). Since aromatic α-keto acids may degrade spontaneously into undesirable flavor compounds, α-hydroxy acid dehydrogenases may be useful in controlling off-flavor development via diversion of chemically labile α-keto acids to more stable a-hydroxy acids. To test this hypothesis, we investigated the effect of D-hydroxyisocaproate dehydrogenase overexpression by a L. casei adjunct on chemical and sensory properties of reduced-fat Cheddar cheese made with and without addition of 20 mM α-ketoglutarate. The D-hydroxyisocaproic acid dehydrogenase gene (D-HicDH) was cloned into a high copy number vector pTRKH2 and transformed into L. casei ATCC334. Reduced-fat Cheddar cheeses were made with Lactococcus lactis starter only, starter + L. casei ATCC334 with pTRKH2, and starter + L. casei ATCC334 with pTRKH2: D-HicDH, and then volatile analysis was performed by gas chromatography and mass spectrometry. Statistical analysis of volatile data after 3 mo of ripening at 7°C showed profiles of ketones, aldehydes, alcohols, esters, sulfur compounds, and benzaldehyde were significantly altered by culture treatments and α-ketoglutarate addition, and these treatments also affected sensory flavor attributes of experimental cheeses. Results also indicated overexpression of D-hydroxyisocaproic acid dehydrogenase can divert labile α-keto acids into more stable compounds, but the overall effect seemed to diminish both beneficial and detrimental flavor notes

Tyrosine and phenylalanine catabolism byLactobacillus cheese flavor adjuncts

Bacterial metabolism of Tyr and Phe has been associated with the formation of aromatic compounds that impart barny-utensil and floral off-flavors in cheese. In an effort to identify possible mechanisms for the origin of these compounds in Cheddar cheese, we investigated Tyr and Phe catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts under simulated Cheddar cheese-ripening (pH 5.2, 4% NaCl, 15°C, no sugar) conditions. Enzyme assays of cell-free extracts indicated that L. casei strains catabolize Tyr and Phe by successive, constitutively expressed transamination and dehydrogenation reactions. Similar results were obtained with L. helveticus strains, except that the dehydrogenase enzymes were induced during incubation under cheese-ripening conditions. Micellar electrokinetic capillary chromatography of supernatants from L. casei and L. helveticus strains incubated under simulated cheese-ripening conditions confirmed that Tyr and Phe transamination and dehydrogenation pathways were active in both species and also showed these reactions were reversible. Major products of Tyr catabolism were p-hydroxy phenyl lactic acid and p-hydroxy phenyl acetic acid, while Phe degradation gave rise to phenyl lactic acid, phenyl acetic acid, and benzoic acid. However, some of these products were likely formed by nonenzymatic processes, since spontaneous chemical degradation of the Tyr intermediate p-hydroxy phenyl pyruvic acid produced p-hydroxy phenyl acetic acid, p-hydroxy phenyl propionic acid, and p-hydroxy benzaldehyde, while chemical degradation of the Phe intermediate phenyl pyruvic acid gave rise to phenyl acetic acid, benzoic acid, phenethanol, phenyl propionic acid, and benzaldehyde

IMMUNOMODULATORY ACTIVITY OF NUTRACEUTICAL FORMULATION AND ITS POTENTIATION BY SELF-FORTIFICATION AND COW URINE DISTILLATE FORTIFICATION METHODS

Objective: This study prepared, evaluated immunomodulatory activity of nutraceutical formulation and studied the effect of self-mortification and cow urine distillate fortification methods on the immunomodulatory potential of nutraceutical formulation.Methods: Three types of nutraceutical formulations i.e. Nutraceutical formulation (NF), self fortitfied nutraceutical formulation (SFNF) and self fortitfied nutraceutical formulation fortified with cow urine distillate (SFNECUD) were prepared using fine powders of amla, apple, garlic, onion, wheat grass, papaya, turmeric and cow urine distillate by different methods. The immunomodulatory activity of nutraceutical formulations at a dose of 500 mg/kg was assessed by various immune function parameters like cell-mediated immunity (neutrophil adhesion, delayed type hypersensitivity (DTH) response and cyclophosphamide-induced neutropenia), humoral immunity (serum immunoglobulins level and haemoagglutination antibody titer), and phagocytic activity (carbon clearance and polymorphonuclear (PMN) cell activity).Results: Oral administration of NF, SFNF and SFNFCUD showed significant (p<0.01) increase in adhesion of neutrophils, potentiation of the DTH reaction and attenuation of cyclophosphamide-induced neutropenia. A significant increase in serum immunoglobulin levels and production of circulating antibody titer in response to sheep red blood cells (SRBCs) was also observed. In addition, an increase in the phagocytic index in carbon clearance assay and an increase in the phagocytic activity of PMN cells was observed.Conclusion: From the above results, it can be concluded that all three types of formulations showed significant immunostimulant activity. SFNF and SFNFCUD showed better immunomodulatory activity than NF suggesting the potentiation of immunomodulatory potential of NF activity by fortification methods

A Review on Present State-of-the-Art of Self Adaptive Dynamic Software Architecture

Enterprises across the world are increasingly depending on software to drive their businesses. It is more so with distributing computing technologies in place that pave way for realization of seamless business integration. On the other hand those complex software systems are expected to adapt changes dynamically without causing administrative overhead. Moreover software systems should exhibit fault tolerance, location transparency, availability, scalability self-adaptive capabilities to fit into present enterprise business use cases. To cope with such expectations software systems are to be built with a dynamic and self-adaptive software architecture which drives home quality of services perfectly. The point made here is that software systems are facing unprecedented level of complexity and aware of self-adaptation. Therefore it is essential to have technical knowhow pertaining to self adaptive dynamic software architecture. Towards this end, we explore present state-of-the-art of this area in software engineering domain. It throws light into dynamic software architectures, distributed component technologies for realizing such architectures, besides dynamic software composition and metrics to evaluate the quality of dynamic adaptation

Myxedema Coma: A Life-Threatening Condition in Patients Using Pembrolizumab

The advent of immune checkpoint inhibitors has significantly improved the prognosis of patients with advanced malignancies. As we begin to understand these medications, multiple immune-related adverse effects (irAEs) have been found with these drugs, including endocrinopathies. Understanding the treatment-related adverse events of these medications is critical for clinical practice. Thyroid-related adverse effects usually occur within the first three months of treatment and rarely after eight months. It can manifest as an early onset of thyrotoxicosis, which is largely asymptomatic, followed by a rapid transition to hypothyroidism, requiring long-term levothyroxine substitution. We present a case in which our patient was found unresponsive, hypothermic, and with respiratory failure almost after completing a year of treatment with pembrolizumab. He had an initial mild elevation in thyroid-stimulating hormone (TSH) of 6.52, although with normal free thyroxine (T4) of 1.06, in his first three months of starting treatment which then rapidly progressed to a true myxedema coma. The infrequency with which this occurs makes it a diagnostic challenge

Leveraging Self-Adaptive Dynamic Software Architecture

Software systems are growing complex due to the technological innovations and integration of businesses. There is ever increasing need for changes in the software systems. However, incorporating changes is time consuming and costly. Self-adaptation is therefore is the desirable feature of any software that can have ability to adapt to changes without the need for manual reengineering and software update. To state it differently robust, self adaptive dynamic software architecture is the need of the hour. Unfortunately, the existing solutions available for self-adaptation need human intervention and have limitations. The architecture like Rainbow achieved self-adaptation. However, it needs to be improves in terms of quality of service analysis and mining knowledge and reusing it for making well informed decisions in choosing adaptation strategies. In this paper we proposed and implemented Enhanced Self-Adaptive Dynamic Software Architecture (ESADSA) which provides automatic self-adaptation based on the runtime requirements of the system. It decouples self-adaptation from target system with loosely coupled approach while preserves cohesion of the target system. We built a prototype application that runs in distributed environment for proof of concept. The empirical results reveal significance leap forward in improving dynamic self-adaptive software architecture

Tryptophan catabolism by Lactobacillus casei andLactobacillus helveticus cheese flavor adjuncts

Microbial degradation of Trp is thought to promote the formation of aromatic compounds that impart putrid, fecal, or unclean flavors in cheese, but pathways for their production have not been established. This study investigated Trp catabolism by Lactobacillus casei and Lactobacillus helveticus cheese flavor adjuncts under carbohydrate starvation (pH 6.5, 30 or 37°C, no sugar) and near cheese-ripening (pH 5.2, 4% NaCl, 15°C, no sugar) conditions. Enzyme assays of cell-free extracts indicated that both species of Lactobacillus catabolized Trp to indole-3-lactic acid, and micellar electrokinetic capillary chromatography of culture supernatants showed this reaction occurred via successive transamination and dehydrogenation reactions. Tryptophan decarboxylase activity was also detected in all Lactobacillus cell-free extracts, but tryptamine was not detected in culture supernatants. Micellar electrokinetic capillary chromatography showed that Trp metabolism in Lactobacillus casei LC301 and LC202 was similar under both incubation conditions and that those catabolic reactions were reversible (i.e., conversion of indole-3-lactic acid to Trp). In contrast, Trp catabolism by Lactobacillus helveticus LH212 was only detected under near cheese ripening conditions. Cells of Lactobacillus helveticus CNRZ32 did not catabolize Trp in either condition but did convert indole-3-pyruvic acid to Trp in carbohydrate starvation medium and to Trp and indole-3-lactic acid under near cheese ripening conditions

Jet fuel based high pressure solid oxide fuel cell system

A power system for an aircraft includes a solid oxide fuel cell system which generates electric power for the aircraft and an exhaust stream; and a heat exchanger for transferring heat from the exhaust stream of the solid oxide fuel cell to a heat requiring system or component of the aircraft. The heat can be transferred to fuel for the primary engine of the aircraft. Further, the same fuel can be used to power both the primary engine and the SOFC. A heat exchanger is positioned to cool reformate before feeding to the fuel cell. SOFC exhaust is treated and used as inerting gas. Finally, oxidant to the SOFC can be obtained from the aircraft cabin, or exterior, or both

A Carbon Corrosion Model to Evaluate the Effect of Steady State and Transient Operation of a Polymer Electrolyte Membrane Fuel Cell

A carbon corrosion model is developed based on the formation of surface oxides on carbon and platinum of the polymer electrolyte membrane fuel cell electrode. The model predicts the rate of carbon corrosion under potential hold and potential cycling conditions. The model includes the interaction of carbon surface oxides with transient species like OH radicals to explain observed carbon corrosion trends under normal PEM fuel cell operating conditions. The model prediction agrees qualitatively with the experimental data supporting the hypothesis that the interplay of surface oxide formation on carbon and platinum is the primary driver of carbon corrosion