Microbial nutrients

The raw materials used in a particular product may present some challenges to the formulation chemist when selecting the most appropriate preservative. Problem ingredients may act as microbial nutrients, preservative inactivators or preservative adsorbers and careful testing and assessment of the preservative system is necessary in these cases. One notable example of this is the inactivation of parabens esters by certain non-ionic surfactants. 

DOM is ubiquitous in rivers, lakes, groundwater, and oceans. It therefore plays a dominant role in the biosphere as well as in treatment of fresh water, for industrial use and human consumption. The main aspects in addition to the function as microbial nutrients are (a) the interactions with other water constituents like metals and xenobiotics and (b) the reactions with chemicals that are used for water disinfection (e.g., chlorine). The latter leads to the problem of disinfection by-product (DBP) formation, which is of toxicological relevance. 

The usual jarosites formed in these situations are hydronium, potassium or ammonium forms in which A is hydrogen, potassium or ammonium ion. In leaching situations, jarosite formation can strip out essential microbial nutrients such as potassium and ammonium ions (Duncan and Walden, 1972 L.A.V. Sulligoi, 1972, personal communication). 

Solutes present (oxygen, carbon dioxide, carbon compounds, nitrogen compounds, other microbial nutrients)... 

Alongi, D.M., Christoffersen, P. and Tirendi, F. (1993) The influence of forest type on microbial-nutrient relationships in tropical mangrove sediments. Journal of Experimental Marine Biology and Ecology, 171, 201-223. 

The quantities of nutrients in microbes are large compared with the annual plant nutrient uptake, suggesting that even relatively limited dieback of the microbial populations can lead to release of an appreciable proportion of the plants annual nutrient requirement. Indeed, it is known that the annual uptake of P by wet tundra vegetation can be almost entirely accounted for by P released through nutrient flushes from the microbial biomass (Chapin et al, 1978). It is possible, therefore, that the supply rate of nutrients to the soil inorganic pool varies depending on the conditions for microbial population growth or decline and that plant nutrient availability fluctuates inversely to microbial nutrient demand. 

Marine microbes are frequently found attached to surfaces, or will attach to a surface given the opportunity. Early studies of marine fouling of glass surfaces were conducted by Zobell (53) and Kriss (54). One of their most important observations was tRat the adsorptTon of organic materials by solid surfaces concentrated microbial nutrients and that this led to colonization. The work of Floodgate (33) and others indicates that while adsorbed layers may stimulate growth, purely physical factors can also dominate the interaction. 

J. E. Haky, andC. Carraher. 1997. Shading of periphyton communities by wetland emergent macrophytes decoupling of algal photosynthesis from microbial nutrient retention. Arch. Hydrobiol. 139 17-27. 

Electrobioremediation Induced Mass Transfer and Transport of Microbial Nutrients and Electron Acceptors... 

Chemical hazards also pose a concern for winemakers. These can be divided into naturally occurring, intentionally added, and unintentional/ incidental. Examples of naturally occurring chemicals that could pose a risk to human health are biogenic amines (Section 11.3.6), ethyl carbamate (11.3.2), and mycotoxins (Section 4.5.2). Intentionally added chemicals include sulfur dioxide (gas, sulfur wicks, or potassium metabisulfite), tartaric acid, Velcorin (Section 5.2.2), and microbial nutrient formulations (diammonium phosphate or proprietary blends). Finally, uninten-tional/incidental chemicals would include residues of agricultural chemicals that exceed approved levels, cleaners or sanitizers (Chapter 9), and the inadvertent transfer of lubricants from equipment. 

Microbial attack of vinyl chloride has been shown to occur (Nelson, Y.M. and Jewell, W.J., 1993) and still further it is known that vinyl acetate breaks down to give acetaldehyde and acetate (Nieder, M., Sunarko, B. and Meyer, O., 1990), both metabolities being microbial nutrients at the concentrations found in typical polymer dispersions, where free vinyl acetate concentrations can be in the order of 0.1%. At higher levels, as may have been found some years ago, acetaldehyde would have been present at preservative concentrations. 

McCLURE G.W. 1970. Accelerated degradation of herbicides in soil by the application of microbial nutrient broths. Contributions from Boyce Thompson Institute, 24, 235-244. 

Plasticizers Polar plasticizers such as esters decrease surface resistivity of nonblack compounds hydrocarbon secondary plasticizers provide increased levels. Unplasticized PVC without a surface coating of paraffin wax has a surface resistivity of about 10 ohm. Addition of 40 phr of ester plastieizer decreases this to 10 °-10 ohm. Phosphate plasticizers can lower surface resistivity by several orders of magnitude. In addition, the mobility (lowering of glass transition temperature) of the plasticizer is a factor. Low-temperature plasticizers are found to have an increased effect in lowering surface resistivity. When substituting, for example, an adipate or oleate for a phthalate to lower surface resistivity (in cases where the application permits), it must be considered that the former are more available microbial nutrients. 

---