Micro-organisms in latex and natural rubber coagula ofHevea brasiliensisand their impact on rubber composition, structure and properties

Abstract

Summary Natural rubber, produced by coagulation of the latex from the tree Hevea brasiliensis, is an important biopolymer used in many applications for its outstanding properties. Besides polyisoprene, latex is rich in many nonisoprene components such as carbohydrates, proteins and lipids and thereby constitutes a favourable medium for the development of micro‐organisms. The fresh rubber coagula obtained by latex coagulation are not immediately processed, allowing the development of various microbial communities. The time period between tree tapping and coagula processing is called maturation, during which an evolution of the properties of the corresponding dry natural rubber occurs. This evolution is partly related to the activity of micro‐organisms and to the modification of the biochemical composition. This review synthesizes the current knowledge on microbial populations in latex and natural rubber coagula of H. brasiliensis and the changes they induce on the biochemistry and technical properties of natural rubber during maturation.

Characterisation of macrogel composition from industrial natural rubber samples: Influence of proteins on the macrogel crosslink density

“…This gel phase is composed of an insoluble fraction called 'macrogel' [11,12], and of microaggregates dispersed in the soluble fraction, called 'microgel' [13,14] (Figure 1). Some non-isoprene compounds of NR, such as lipids (1.5-4% w/w) [4,[15][16][17], proteins (1-3.5% w/w) [4,[17][18][19], and minerals (0.2% w/w) [4,20], are assumed to be responsible for the existence of this gel phase. For example, macrogel can be eliminated by transesterification or deproteinization of NR.…”

Microbial communities in natural rubber coagula during maturation: impacts on technological properties of dry natural rubber

“…), fresh latex was characterized by a higher content of Lactococcus (48%) and Enterobacteria (12%), which is concordant with previous studies (Salomez et al . ). Community structures of inoculum 1 and inoculum 2 were significantly different.…”

“…This poorly characterized step is indeed critical in the production of commercial NR as it affects its technological properties (Salomez et al . ).…”

“…Micro‐organisms are already present in the latex vessels of tapped trees and in harvested latex, with total concentrations of 10 5 –10 7 CFU per ml (Salomez et al . ). Previous studies have identified Bacillus , Lactococcus , Enterobacter , Serratia , Streptomyces and Micrococcus as main bacterial genera (Taysum ; Shum and Wren ; Intapun et al .…”

“…Modifications of the technological properties of NR during maturation have been linked to the presence of micro‐organisms (Salomez et al . ) especially its initial Wallace plasticity ( P 0 ) and its resistance to thermo‐oxidation (PRI). Indeed, the use of antimicrobial agents has a strong stabilizing effect on NR properties (Varghese et al .…”