The effect of lactic acid on the outer membrane permeability of Escherichia coli O157:H7, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhimurium was studied utilizing a fluorescent-probe uptake assay and sensitization to bacteriolysis. For control purposes, similar assays were performed with EDTA (a permeabilizer acting by chelation) and with hydrochloric acid, the latter at pH values corresponding to those yielded by lactic acid, and also in the presence of KCN. Already 5 mM (pH 4.0) lactic acid caused prominent permeabilization in each species, the effect in the fluorescence assay being stronger than that of EDTA or HCl. Similar results were obtained in the presence of KCN, except for P. aeruginosa, for which an increase in the effect of HCl was observed in the presence of KCN. The permeabilization by lactic and hydrochloric acid was partly abolished by MgCl2. Lactic acid sensitized E. coli and serovar Typhimurium to the lytic action of sodium dodecyl sulfate (SDS) more efficiently than did HCl, whereas both acids sensitized P. aeruginosa to SDS and to Triton X-100. P. aeruginosa was effectively sensitized to lysozyme by lactic acid and by HCl. Considerable proportions of lipopolysaccharide were liberated from serovar Typhimurium by these acids; analysis of liberated material by electrophoresis and by fatty acid analysis showed that lactic acid was more active than EDTA or HCl in liberating lipopolysaccharide from the outer membrane. Thus, lactic acid, in addition to its antimicrobial property due to the lowering of the pH, also functions as a permeabilizer of the gram-negative bacterial outer membrane and may act as a potentiator of the effects of other antimicrobial substances.

https://www.thermoscientific.com/content/dam/tfs/LPG/LCD/LCD%20Documents/Peer%20Reviewed%20Papers%20OR%20Third-Party%20Papers/Microplate%20Instrumentation/Microplate%20Readers/D00570~.pdf

Lactic acid permeabilizes gram-negative bacteria by disrupting the outer membrane

Fungi are an understudied, biotechnologically valuable group of organisms. Due to 
the immense range of habitats that fungi inhabit, and the consequent need to compete against a diverse array of other fungi, bacteria, and animals, fungi have developed numerous survival mechanisms. The unique attributes of fungi thus herald great promise for their application in biotechnology and industry. Moreover, fungi can be grown with relative ease, making production at scale viable. The search for fungal biodiversity, and the construction of a living fungi collection, both have incredible economic potential in locating organisms with novel industrial uses that will lead to novel products. This manuscript reviews fifty ways in which fungi can potentially be utilized as biotechnology. We provide notes and examples for each potential exploitation and give examples from our own work and the work of other notable researchers. We also provide a flow chart that can be used to convince funding bodies of the importance of fungi for biotechnological research and as potential products. Fungi have provided the world with penicillin, lovastatin, and other globally significant medicines, and they remain an untapped resource with enormous industrial potential.

The amazing potential of fungi: 50 ways we can exploit fungi industrially

Commercial production of carotenoids from microorganisms competes mainly with synthetic manufacture by chemical procedures. Efficient stimulation of carotenoid biosynthesis is expected to promote accumulation of carotenoid by microbes. This review describes the variety of environmental and cultural stimulants studied during the last few decades which enhance volumetric production and cellular accumulation of commercially important carotenoids from microalgae, fungi and bacteria. Stimulation of carotenoid production by white-light illumination and temperature fluctuation is discussed along with supplementation of metal ions, salts, organic solvents, preformed precursors and several other chemicals in the culture broth. Reports on the improvements in yield are reviewed and assessed from a biotechnology point of view.

Environmental and cultural stimulants in the production of carotenoids from microorganisms.

One stop mycology

https://backend.orbit.dtu.dk/ws/files/161201597/1_s2.0_S109671761830288X_main.pdf

Lipid engineering combined with systematic metabolic engineering of Saccharomyces cerevisiae for high-yield production of lycopene

Aspergillus nigerconidia are characterized by exogenous dormancy: the first stage of their germination is accomplished in twice-distilled water. However, germ tube formation requires the availability of carbon and nitrogen sources. Exogenous dormancy in A. nigerconidia exhibits the following peculiar features: (i) nitrogen-containing substances are active stimulators of germination; (ii) temperature-dependent changes in the lipid bilayer and in the neutral lipid composition of conidia are virtually identical to those occurring in growing mycelium under temperature stress; and (iii) the spore viability threshold does not exceed 45°C; i.e., the spores are more heat-resistant than the mycelium, but they are less heat-resistant than the spores that are in the state of endogenous dormancy. According to the current classification of the types of cell metabolism arrest, the exogenous dormancy of A. nigerconidia resembles the pattern of metabolism characteristic of vegetative cells during the idiophase.

Peculiarities of Exogenous Dormancy of Aspergillus nigerConidia

Comparison of the changes in the composition of the membrane lipids and soluble cytosol carbohydrates caused by two types of heat influence (within the tolerance zone and heat shock-level) revealed fundamental differences in the stress response of fungal cells. In three fungal species, Aspergillus niger, Pleurotus ostreatus, and Cunninghamella japonica, increased levels of trehalose and phosphatidic acids were observed under heat shock, while heat influences within the tolerance zone had no such effect. Under heat shock, the ratio of saturated fatty acids did not increase in any of the major phospholipids of all the studied species. This is in contradiction with the existing hypothesis and confirms the previously suggested the hypothesis of membrane stabilization by heat-protecting compounds.

The effect of different heat influences on composition of membrane lipids and cytosol carbohydrates in mycelial fungi

The change of the content and composition of the chitin-glucan complex (CGC) of the ascomycete Aspergillus niger during its development has been studied. In submerged mycelium, the complex is dominated by glucan, whereas chitin is predominant in sporophores and spores. The highest CGC content has been noted in sporophores in the terminal phase and in submerged mycelium in the idiophase; i.e., before the formation of dormant cells. On the grounds of the correlation of the content and composition of lipids, protecting carbohydrates, and CGC, it is suggested that cell wall structural polysaccharides are involved in biochemical adaptation to adverse factors.

Developmental change of the composition and content of the chitin-glucan complex in the fungus Aspergillus niger

Stimulation of lycopene synthesis in the mycelium of the mucoraceous fungus Blakeslea trispora was accompanied by major changes in its lipid composition The phospholipid content in the membrane lip-ids doubled, whereas the sterol and sphingolipid levels changed insignificantly The amounts of phosphatidyl-choline, phosphatidylethanolamine, and phosphatidic acid in the phospholipids and the triacylglycerol content in the acylglycerols increased The desaturation degree of fatty acids drastically increased against the background of a decrease in that of the neutral lipids The data obtained are discussed in relation to the mechanism of action of the lycopene formation stimulator

Lipid composition of the mucoraceous fungus Blakeslea trispora under lycopene formation-stimulating conditions.

This article deals with the lycopene of mycelial fungi. It pays special attention to its physical and chemical properties, occurrence in nature, biological functions, and the biotechnology of lycopene production. Data are presented concerning the medically important properties of lycopene and the drug Mycolycopene prepared on its basis. Its prospective use in the therapy of prostate cancers is discussed.

A. S. Memorskaya

Papers

Peculiarities of Exogenous Dormancy of Aspergillus nigerConidia

The effect of different heat influences on composition of membrane lipids and cytosol carbohydrates in mycelial fungi

Developmental change of the composition and content of the chitin-glucan complex in the fungus Aspergillus niger

Lipid composition of the mucoraceous fungus Blakeslea trispora under lycopene formation-stimulating conditions.

[Fungal lycopene: the biotechnology of its production and prospects for its application in medicine].