Sphagnan - a pectin-like polymer isolated fromSphagnummoss can inhibit the growth of some typical food spoilage and food poisoning bacteria by lowering the pH

Abstract

Aims: Investigate if the antibacterial effect of sphagnan, a pectin‐like carbohydrate polymer extracted from Sphagnum moss, can be accounted for by its ability to lower the pH. Methods and Results: Antibacterial activity of sphagnan was assessed and compared to that of three other acids. Sphagnan in its acid form was able to inhibit growth of various food poisoning and spoilage bacteria on low‐buffering solid growth medium, whereas sphagnan in its sodium form at neutral pH had no antibacterial activity. At similar acidic pH, sphagnan had comparable antibacterial activity to that of hydrochloric acid and a control rhamnogalacturonan pectin in its acid form. Conclusions: Sphagnan in its acid form is a weak macromolecular acid that can inhibit bacterial growth by lowering the pH of environments with a low buffering capacity. Significance and Impact of the Study: It has previously been suggested that sphagnan is an antimicrobial polysaccharide in the leaves of Sphagnum moss with a broad range of potential practical applications. Our results now show that sphagnan in its acid form can indeed inhibit bacterial growth, but only of acid‐sensitive species. These findings represent increased knowledge towards our understanding on how sphagnan or Sphagnum moss might be used in practical applications.

Biochemical determinants of litter quality in 15 species of Sphagnum

“…cell-wall polysaccharides (Turetsky et al 2008), especially the pectic cell-wall polysaccharide Bsphagnan^ (Painter 1991;Børsheim et al 2001;Painter 2003;Hájek et al 2011), to be the main compound influencing litter quality in Sphagnum. Although the antimicrobial properties of sphagnan were attributed to acidification (Ballance et al 2007;Stalheim et al 2009), sphagnan addition has been found to block nitrogen mineralisation of plant litters (Hájek et al 2011). Hájek et al (2011) interpreted such active inhibition of microbial decay as electrostatic inactivation of microbial extracellular enzymes by the negatively charged sphagnan polymer (Ballance et al 2008).…”

Polysaccharides from Lower Plants: Bryophytes

“…There have also been some investigations of a possibility that when the Sphagnum moss cell wall dies, synthesis of hyaline is induced as a result of water consumption in the cell, and the concentration of galacturonic acid increases, resulting in the growth of the inner cell pH levels, eventually causing the antimicrobial effect of moss (Balance et al 2012). However, it should be noted that this theory applies to acid-sensitive bacteria only (Painter 1991;Stalheim et al 2009). Although sphagnan has antimicrobial activity, its practical usage in food preservation is uncertain, because, even though the outer layers of products are preserved, inner spoilage is possible for the reason that soluble proteins diffuse from muscles too quickly and neutralize the active carbonyl groups, thereby causing spoilage from inside of the food product (Borsheim et al 2001;Stalheim et al 2009).…”

“…Some studies claim that the antimicrobial activity of peat in bogs occurs due to the low pH and anoxic conditions that are caused by humic substances, although this argument cannot be considered fully true, as there have been acidophilic, anaerobic bacteria found that could easily survive in this kind of environment (Painter 1991). Nevertheless, some scientists believe that the main reason for the antimicrobial activity of sphagnan is related to its acidic properties that lower the pH level of bog waters (Stalheim et al 2009). There have also been some investigations of a possibility that when the Sphagnum moss cell wall dies, synthesis of hyaline is induced as a result of water consumption in the cell, and the concentration of galacturonic acid increases, resulting in the growth of the inner cell pH levels, eventually causing the antimicrobial effect of moss (Balance et al 2012).…”

“…Major growth of interest in bryophyte and, specifically, Sphagnum moss polysaccharides happened after the discovery that the Sphagnum moss polysaccharides can be used for preservation of food articles (Stalheim et al 2009;Borsheim et al 2001;Painter 1998Painter , 1991. This concept largely relies on the widespread use of Sphagnum mosses for food preservation in traditional cultures of northern countries.…”

Biochemical and structural controls on the decomposition dynamics of boreal upland forest moss tissues

“…primarily of rhamnose, mannose, and galacturonic acid (Ballance et al, 2007). This mixture appears to be resistant to decomposition and/or possess antimicrobial properties (Hájek et al, 2011;Stalheim et al, 2009). While this fraction has only been identified in Sphagnum, uronic acid-enriched carbohydrates in these upland mosses could play a similar role.…”