PMC

Salmonella biofilm on crumb rubber. (A) Crumb rubber that was not inoculated with bacteria; (B) crumb rubber inoculated with a 5% inoculation of Salmonella. The blue color is the surface of crumb rubber, and green is the nucleic acid (stained with SYTO 13) of bacterial cells.

The bond-breaking positions of hydrogen in (a) syringic acid, (b) erucic acid, and (c) natural rubber repeat unit.

The metabolic route map for natural rubber (cis‐1,4‐polyisoprene) biosynthesis in plants, including the pathways for substrate synthesis, and their locations. Isopentenyl pyrophosphate (IPP), the monomeric subunit for rubber biosynthesis (orange arrow) is synthesized by two pathways, the mevalonic acid pathway (MVA, cytosolic, green arrows and numerals) and the methylerythritol pathway (MEP, plastidic, red arrows and lower case letters) from acetyl‐CoA or glyceraldehyde‐3‐phosphate and pyruvate, respectively. IPP and its stereoisomer dimethylallyl pyrophosphate (DMAPP) condense to form several allylic pyrophosphates (APPs), namely geranyl pyrophosphate (GPP, C₁₀), farnesyl pyrophosphate (FPP, C₁₅) and geranyl geranyl pyrophosphate (GGPP, C₂₀). These APPs can be used as rubber chain initiators (blue arrow), FPP being the most common initiator, and are also the building blocks for terpenes such as chlorophyll, sterols, plant growth regulators, essential oils and so forth. Natural rubber biosynthesis is catalysed by rubber transferase complexes (magenta) bound to the proteolipid uni‐lamella membrane (light blue) of cytosolic rubber particles, and rubber is compartmentalized to the rubber particle interior. Key: MVA enzymes: PDC, pyruvate dehydrogenase complex; AACT, acetyl coenzyme A acetyltransferase; HMGS, hydroxymethylglutaryl coenzyme A synthase; HMGR, hydroxymethylglutaryl coenzyme A reductase; MK, mevalonate kinase; PMK, phosphomevalonate kinase; MDC, diphosphomevalonate decarboxylase. MVA substrates: 1. pyruvate; 2. acetyl coenzyme A; 3. acetoacetyl coenzyme A; 4. hydroxymethylglutaryl coenzyme A; 5. mevalonate; 6. phosphomevalonate; 7. diphosphomevalonate. MEP enzymes: DXS, 1‐deoxy‐_D‐xylulose 5‐phosphate synthase; DXR, 1‐deoxy‐_D‐xylulose 5‐phosphate reductoisomerase; MCT, 2‐C‐methyl‐D‐erythritol 4‐phosphate cytidylyltransferase; CMK,4‐(cytidine 5^/‐diphospho)‐2‐C‐methyl‐D‐erythritol kinase; MDS, 2‐C‐methyl‐D‐erythritol 2,4‐cyclodiphosphate synthase; HDS, 4‐hydroxy‐3‐methylbut‐2‐enyl diphosphate synthase; HDR, 4‐hydroxy‐3‐methylbut‐2‐enyl diphosphate reductase. MEP substrates: a+, pyruvate and D‐glyceraldehyde 3‐phosphate; b. 1‐deoxy‐D‐xylulose 5‐phosphate; c. 2‐C‐methyl‐D‐erythritol 4‐phosphate; d. 4‐(cytidine 5^/‐diphospho)‐2‐C‐methyl‐D_‐erythritol; e. 2‐phospho‐4‐(cytidine 5^/‐diphospho)‐2‐C‐methyl‐D‐ erythritol; f. 2‐C‐methyl‐D_‐erythritol 2,4‐cyclodiphosphate; g. (E)‐4‐hydroxy‐3‐methylbut‐2‐enyl diphosphate. RP, rubber particle; RT‐ase, rubber transferase complex; P, non‐RT‐ase rubber particle‐associated proteins; complexes; PL, proteolipid unilamella membrane; NR, natural rubber polymers.

Mass spectrum of biodiesel from rubber seed oil. a Linoleic acid methyl ester (33.43%), b oleic acid methyl ester (29.73%), c palmitic acid methyl ester (12.59%), d stearic acid methyl ester (8.35%) and e linolenic acid methyl ester (15.90%)