Aerobic Decomposition of Guayule Shrub ( Parthenium argentatum Gray)

Abstract

INTRODUCTIONAerobic microbial decomposition of guayule shrub (Parthenium argentatum Gray) by natural flora has recently been investigated as part of the research program dealing with natural rubber carried out at this Laboratory. In the course of this work, we obtained data of general interest on the broad problem of the aerobic decomposition of woody tissue by natural flora and the biochemical changes thus produced. Only those changes taking place in the first two or three weeks were investigated, because such periods appear to be as long as would be industrially feasible in rubber recovery. The data obtained show that under proper conditions a marked disintegration of the tissue can be brought about in one to two weeks. Aspects of the problem which bear upon the technology of guayule rubber will be presented elsewhere at a later date.Decomposition of plant materials by microorganisms has been studied extensively in relation to soil fertility, peat formation, and manures. The voluminous literature on this subject has been reviewed by Waksman (1932, 1940). With few exceptions emphasis has been placed primarily on the changes in the material undergoing decomposition and secondarily upon the agents bringing them about.Guayule is a small, profusely branching shrub which is native to the plateau of northern Mexico and the southwestern part of the United States. The ecology and anatomy of the plant were extensively investigated by Lloyd (1911). Certain aspects of the anatomy of the plant have been further investigated recently by Artschwager (1943).The aerobic decomposition of whole and defoliated guayule was employed by Spence (1933) to improve the quality of rubber recovered in the industrial milling process. The agents responsible for the changes were not investigated, but from the nature of the environment, such as high moisture, and from the resulting effects (thermogenesis, ammonia production, etc.) it can be assumed that they were microbial. He called this process "retting." Although the term cannot be used here in its strict sense as applied to flax, it does signify that the changes are microbiological and is so used in this paper. METHODS Preparation of shrubThe air-dry, two-year-old shrub was mechanically defoliated and cut in 1to 2-inch lengths in an ensilage cutter. It was then passed through a cane mill in which pieces larger in diameter than one-quarter inch were crushed to about this thickness and many of the smaller pieces were cracked. The shrub treated in this way had a density of about 16 pounds per cubic foot on a dry-weight basis, or 46 pounds per cubic foot at 65 per cent moisture. The resultant air space in the mass at 65 per cent moisture, assuming a density of 1 for the wet shrub, was about 25 per cent of the volume occupied by the shrub.Sampling and analysisChemical. The prepared shrub was riffled to a 1to 2-per cent sample, which was cut fine, mixed, and used for chemical analysis. The retting shrub was sampled by removing the entire charge and mixing it thoroughly, then removing about 70 po...

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“…This process, known as retting, was applied to reduce the content of terpene resins prior to the extraction of natural rubber for the industrial production of latex ( Allen etal. 1944 ; Naghski etal. 1944 ).…”

“…1944 ). It involved a prior treatment of milled guayule shrubs in boiling water both to remove surface matter and to hydrate/soften the plant tissues, followed by the aerobic decomposition under high moisture of the resulting plant material by the prolific microbiota that survived the above treatment and which was located primarily within the bark ( Naghski etal. 1944 ).…”

“…We traced in this work the origins of the A. baumannii DSM30011 collection strain to an isolate first reported in 1944 obtained from retting enrichment of the natural microbiota associated to a resin-producing desert shrub, guayule ( Allen etal. 1944 ; Naghski etal. 1944 ).…”

“…This strain was isolated after enrichment of the resin-degrading natural microbiota responsible of the aerobic decomposition of guayule ( Parthenium argentatum Gray), a resin-producing angiosperm of the Asteraceae family common to arid and semiarid areas of the south-western United States and north-central Mexico ( Allen etal. 1944 ; Naghski etal. 1944 ).…”

Acinetobacter baumannii NCIMB8209: a Rare Environmental Strain Displaying Extensive Insertion Sequence-Mediated Genome Remodeling Resulting in the Loss of Exposed Cell Structures and Defensive Mechanisms

“…We have recently traced the origins of the collection strain A. baumannii DSM30011 ( 11 ) to an isolate originally classified as Achromobacter lacticum , which was obtained prior to 1944 from the enriched microbiota responsible for the aerobic decomposition of the resinous desert shrub guayule ( 14 , 15 ). WGS of this strain and subsequent comparative analysis with 32 other complete clinical A. baumannii genomes revealed the presence of 12 unique accessory chromosomal regions in strain DSM30011, including five regions containing phage-related genes, five regions encoding toxins related to the type 6 secretion system, and one region encompassing a novel CRISPR-cas cluster ( 11 ).…”