Paenibacillus macerans

Other Names

Aerobacillus maceransAerobacillus schuylkilliensisBacillus acetoethylicumBacillus betanigrificansBacillus maceransBacillus soliBacillus vagansBactrillum maceransPaenibacillus thermophilusZymobacillus macerans

Synopsis

Paenibacillus macerans: A Comprehensive Reference

1. Identity and Classification

1.1 Taxonomic Names and Synonymy

Paenibacillus macerans is a diazotroph bacterium found in soil and plants, capable of nitrogen fixation and fermentation, originally discovered in 1905 by an Austrian biologist named Schardinger and initially classified as a bacillus. Its formal taxonomic designation is Paenibacillus macerans (Schardinger 1905) Ash et al. 1994, with NCBI Taxonomy ID 44252.

The organism has accumulated numerous historical synonyms through successive reclassifications. These include Bacillus macerans (Schardinger 1905), Aerobacillus macerans (Schardinger 1905) Donker 1926, Zymobacillus macerans (Schardinger 1905) Kluyver and van Niel 1936, Bactrillum macerans (Schardinger 1905) Pribram 1933, and Bacillus acetoethylicum Northrop et al. 1919. The species was previously widely reported in the scientific literature under the name Bacillus macerans (EFSA BIOHAZ Panel, 2016).

Paenibacillus is a genus originally included within Bacillus and then reclassified as a separate genus in 1993; the genus name reflects the Latin paene, meaning "almost," so paenibacilli are literally "almost bacilli."

1.2 Full Taxonomy

The organism belongs to Phylum Bacillota (Firmicutes), Class Bacilli, Order Caryophanales, Family Paenibacillaceae, Genus Paenibacillus. The type strain of Bacillus macerans is deposited under reference collections including ATCC 8244, DSM 24, JCM 2500, NCIMB 9368, NCTC 6355, and others.

1.3 Morphology and Microbiological Characteristics

P. macerans is part of the family Paenibacillaceae and is a facultative anaerobe. It is gram-variable, being gram-positive or gram-negative rods. It does not have a capsule, and it possesses peritrichous flagella for movement. It forms ellipsoidal, terminal, or subterminal spores which may persist in the soil for many years.

In the laboratory, P. macerans can be grown on nutrient agar with a slightly acidic pH around 5. Its optimal growth temperature is 30 °C, and it shows no growth in 5% NaCl.

1.4 Natural Habitat and Sources

Paenibacillus macerans is a diazotroph bacterium found in soil and plants, capable of nitrogen fixation and fermentation. It forms ellipsoidal, terminal, or subterminal spores which may last in the soil for many years. The bacterium is usually found in soil and plant materials, but has also been identified in blood cultures of infants with infection. It multiplies in plant materials at elevated temperatures, and spores are relatively scarce in soil. One strain has also been isolated from chicken eggs.

1.5 Common Forms and Preparations

As a microorganism that does not hold any established status as a conventional food or dietary supplement ingredient intended for direct human ingestion, P. macerans is encountered in several indirect forms in commerce and research:

Cyclodextrin glucanotransferase (CGTase) enzyme preparations: At the beginning of the 20th century, Franz Schardinger isolated cyclodextrins from starch digested by Bacillus macerans; B. macerans (now P. macerans) is still among the most commonly used bacterial species for the production of CGTase to form cyclodextrins.
Cyclodextrins (Schardinger dextrins): The Schardinger dextrins are a group of homologous oligosaccharides obtained from the breakdown of starch by the action of Bacillus macerans amylase. These cyclodextrins are widely used as food-grade excipients and nutraceutical delivery vehicles.
Exopolysaccharide (EPS) preparations: Exopolysaccharides (EPSs) from Paenibacillus spp., including from strains of P. macerans, have been investigated with respect to production, purification, structure, and bioactivity.
Agricultural inoculants (biofertilizer): Selected strains are applied as biological fertilizers, exploiting the organism's nitrogen-fixing capabilities.

2. Historical and Scientific Background

2.1 Discovery and Early Characterization (1904–1950s)

In 1904, Schardinger isolated a new organism capable of producing acetone and ethyl alcohol from sugar and starch-containing plant material. In 1911, he described that this strain, called Bacillus macerans, also produces large amounts of crystalline dextrins (25–30%) from starch. Schardinger named his crystalline products "crystallised dextrin α" and "crystallised dextrin β." It took until 1935 before γ dextrin was isolated.

Franz Schardinger, an Austrian microbiologist, first isolated two crystalline substances from Bacillus macerans in a starch medium, naming them crystalline dextrin A and B. It was not until the 1930s that research into cyclodextrins progressed, and Freudenberg and French's work on the structure of "Schardinger dextrins" in the 1940s led to the discovery of γ-cyclodextrin and subsequently solved the cyclic oligosaccharide structure of cyclodextrins.

In 1949, Dr. French also observed an interesting feature: after a few days, the cycloamyloses formed under the action of Bacillus macerans amylase gradually disappeared. A similar observation had previously been published in 1945 by Cori and Myrbäck. The reducing values and amounts of fermentable sugars gradually increased during enzymolysis of starch with Bacillus macerans amylase preparations.

2.2 Reclassification into Paenibacillus

Several species of Paenibacillus were reclassified immediately after discovery of the genus. Paenibacillus macerans was previously reported as Bacillus macerans (EFSA BIOHAZ Panel, 2016). The formal reclassification to Paenibacillus macerans was made by Ash, Priest and Collins in 1994–1995, based on 16S rRNA gene sequence analysis.

2.3 Traditional and Historical Use

Paenibacillus macerans does not appear in any formally documented traditional or ethnobotanical medical systems (such as Ayurveda, Traditional Chinese Medicine, or European herbal traditions) as an intentional therapeutic or dietary preparation. The organism's recorded history is one of scientific discovery, primarily in the context of industrial microbiology, fermentation science, and soil ecology rather than deliberate human consumption.

The historical significance of P. macerans lies almost exclusively in its role as the founding organism of cyclodextrin chemistry. The Austrian microbiologist Franz Schardinger, later known as the "founding father" of cyclodextrin chemistry, isolated cyclodextrins, which he termed "crystalline dextrins," from several sources of starch following digestion by Bacillus macerans. The Schardinger dextrins are a group of homologous oligosaccharides obtained from the breakdown of starch by the action of Bacillus macerans amylase. They bear the name "Schardinger" in recognition of the fact that Schardinger first identified Bacillus macerans and first described their preparation and properties in reliable detail. The Bacillus macerans enzyme is distinctive in that it degrades starch with the production of almost no reducing power.

In the context of food microbiology, B. macerans (as it was then known) was documented from at least 1994 as an organism naturally occurring in food fermentation environments — specifically in aged Italian cheeses — where its presence was associated with biogenic amine (histamine) production rather than any intentional beneficial use.

3. Key Constituents and Active Compounds

3.1 Cyclodextrin Glucanotransferase (CGTase, EC 2.4.1.19)

Cyclodextrin glucanotransferase (CGTase; EC 2.4.1.19) is a member of the α-amylase family of glycosyl hydrolases (family 13) and is an important enzyme with multiple functions in the starch utilization pathway of some bacteria, catalyzing various glucan-transferring reactions with starch to produce cyclodextrins.

CGTase is also widely applied in baking and carbohydrate glycosylation because it participates in various types of catalytic reactions. The action of CGTase begins with cleavage of an α-1,4-linkage within the glucan molecule.

CGTase is an industrially important enzyme for α-, β-, or γ-cyclodextrin (CD) production, which is extensively used in agriculture, chemicals, cosmetics, foods, and pharmaceuticals.

3.2 Cyclodextrins (Schardinger Dextrins)

Cyclodextrins are a family of cyclic oligosaccharides composed of α-(1,4)-linked glucopyranose subunits. Their production is catalyzed by cyclomaltodextrin glucanotransferase, which degrades starch. There are three naturally existing cyclodextrins — the α-, β-, and γ-cyclodextrins (α-CD, β-CD, and γ-CD) — which consist of six, seven, and eight glucopyranose units, respectively.

The most important property of cyclodextrins is the ability to establish specific interactions — molecular encapsulation — with various types of molecules through the formation of non-covalently bonded entities, either in the solid phase or in aqueous solution, taking up a whole molecule, or some part of it, into their cavities. This process in part mimics the "lock and key" mechanism of enzyme catalysis. Complexation may cause changes in physicochemical properties of the guest molecule, such as solubility, stability, kinetics, bioavailability, and toxicity.

3.3 Exopolysaccharides (EPSs)

Strain TKU029 of P. macerans can produce exopolysaccharides (EPSs; 3.46 g/L) and a biosurfactant (1.78 g/L) in a medium with squid pen powder as the sole carbon/nitrogen source.

The exopolysaccharides (EPS) of Paenibacillus strains have antioxidant and anti-tumour properties, while mutanase enzymes may help to reduce tooth decay. Microbial EPSs are water-soluble polymers that attach to the cell surfaces or are released into the medium. Strains of Paenibacillus produce EPSs with varying characteristics that may be medically useful.

3.4 Biosurfactants

The biosurfactant produced by P. macerans TKU029 can reduce the surface tension of water from 72.30 to 35.34 mN/m at a concentration of 2.76 g/L, reaching an emulsification index of 56% after a 24-hour reaction with machine oil. This biosurfactant is stable at 121 °C for 20 minutes, over a pH range from 3 to 11, and in salt solutions below 5%.

3.5 Histamine

P. macerans also produces a significant amount of histamines, which may cause allergies in some individuals if ingested. The histamine activity of Bacillus macerans isolated from Italian cheese during seasoning was described, with histamine formation detected at all temperatures studied (43, 37, 30, 22, and 4 °C). The maximum histamine formation and the maximum bacterial growth were detected at 30 °C, with 4285 μg of histamine per mL of quantification broth.

3.6 Fermentation Metabolites

Crystalline (Schardinger) dextrins are produced typically from starch. Ethanol and acetic acid are produced in the early stages of glucose fermentation, followed by the disappearance of formate and acetate with gas (H₂) and acetone production. Through fermentation of glycerol, the organism produces ethanol, formate, acetate, succinate, and 1,2-propanediol (1,2-PDO) as fermentation products.

4. Metabolic Capabilities and Established Mechanisms

4.1 Extraordinarily Broad Substrate Range

Paenibacillus macerans is one of the species with the broadest metabolic capabilities in the genus Paenibacillus, able to ferment hexoses, deoxyhexoses, pentoses, cellulose, and hemicellulose. Previously called Bacillus macerans and Bacillus acetoethylicum, it is a gram-positive, spore-forming bacterium capable of fermentative metabolism of this wide array of substrates.

4.2 Glycerol Fermentation

Glycerol was historically considered a nonfermentable carbon source for P. macerans. This "nonfermentable status" was used to determine whether certain electron acceptors, such as fumarate, trimethylamine N-oxide, nitrate, and nitrite, can mediate anaerobic respiration in this organism. However, research found that several P. macerans strains are able to ferment glycerol in the absence of external electron acceptors. The fermentation of glycerol by one of these strains, P. macerans N234A, occurred at high metabolic rates and in the absence of an active 1,3-PDO pathway.

4.3 Nitrogen Fixation (Diazotrophy)

P. macerans is a facultative anaerobe capable of nitrogen fixation; in the absence of oxygen, it is able to convert nitrogen gas to ammonia, which is more easily used by plants. Nitrogen fixers such as P. azotofixans, P. macerans, P. polymyxa, P. graminis, and P. odorifer contain the nifH gene.

4.4 CGTase Enzyme Mechanism

Cyclodextrins can be produced enzymatically from starch and other related carbohydrates using cyclodextrin glucanotransferase (CGTase) via intramolecular transglycosylation, called the cyclization reaction. P. macerans CGTase can transform L-ascorbic acid (L-AA, vitamin C) to 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G), a compound with diverse applications in food, cosmetic, and pharmaceutical industries.

4.5 Antimicrobial Biosurfactant Action

The biosurfactant produced by P. macerans TKU029 shows significant antimicrobial activity, which remains active after treatment at 121 °C and at pH values from 4 to 10, against Escherichia coli BCRC13086, Staphylococcus aureus BCRC10780, Fusarium oxysporum BCRC32121, and Aspergillus fumigatus BCRC30099.

5. Scientific Evidence by Area of Investigation

Important caveat on evidence level: Paenibacillus macerans itself has not been the subject of controlled human clinical trials as a dietary supplement or probiotic agent. All evidence pertaining to the organism as an entity of potential health interest is derived from in vitro (cell culture or biochemical) and, to a limited extent, preclinical (animal or environmental) studies. No peer-reviewed randomized controlled trials (RCTs) in humans assessing the direct administration of P. macerans as a health supplement have been identified in the literature.

5.1 Skin Hydration (Cosmetic/Topical — In Vivo Pilot Data)

Human skin shows from 37.3 to 44.3% hydration after being treated with TKU029 EPSs for 180 minutes. The EPS produced by P. macerans TKU029 can increase in vivo skin hydration and may represent a new source of natural moisturizers with potential value in cosmetics. The untreated control revealed an increase in skin hydration after 180 minutes of 8.1% for TKU029 EPSs and of approximately 0.8% for hyaluronic acid; EPSs produced by P. macerans TKU029 can increase in vivo skin hydration.

Evidence assessment: This is a single-strain in vivo pilot measurement on human skin, not a controlled clinical trial. It is insufficient to make therapeutic or health claims. It is classified as preliminary evidence warranting further controlled investigation.

5.2 Antimicrobial Activity (In Vitro Only)

As described in Section 4.5, the biosurfactant fraction of P. macerans TKU029 demonstrated antimicrobial activity against both Gram-negative bacteria (E. coli), Gram-positive bacteria (S. aureus), and fungal species (F. oxysporum, A. fumigatus) under in vitro conditions. These results were obtained in laboratory broth and plate assays only. No human clinical data on the antimicrobial efficacy of P. macerans-derived biosurfactants exists in the peer-reviewed literature at this time.

5.3 Antioxidant Properties of Exopolysaccharides (In Vitro)

Paenibacillus exopolysaccharides (EPS) have antioxidant and anti-tumour properties according to in vitro studies, while mutanase enzymes may also help to reduce tooth decay. These properties have been demonstrated in biochemical assays; no in vivo or human data are available for P. macerans EPS specifically.

5.4 Cyclodextrin Production and Nutraceutical Delivery (Industrial/Pharmaceutical Context)

While P. macerans itself is not administered for health purposes, the cyclodextrins it produces via its CGTase enzyme are extensively used in pharmaceutical and nutraceutical applications as encapsulation or delivery vehicles. The most important property of cyclodextrins is the ability to establish specific interactions — molecular encapsulation — with various types of molecules through the formation of non-covalently bonded entities, either in the solid phase or in aqueous solution. This process in part mimics the "lock and key" mechanism of enzyme catalysis. Complexation may cause changes in physicochemical properties of the guest molecule, such as solubility, stability, kinetics, bioavailability, and toxicity.

Studies have been presented where the complexation of natural compounds such as propolis and dietary plant bioactives (e.g., tocotrienol, pentacyclic triterpenoids, curcumin) with γ-cyclodextrin resulted in improved stability, bioavailability, and bioactivity in various laboratory model organisms and in humans. The health relevance of this work, however, is attributed to the cyclodextrin molecules themselves — not to the bacterium that produces the CGTase enzyme used in their manufacture.

5.5 Vitamin C Stabilization: Glucosylated Ascorbic Acid (AA-2G) (In Vitro/Industrial)

CGTase of P. macerans can transform L-ascorbic acid (L-AA, vitamin C) to 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G), which shows diverse applications in food, cosmetic, and pharmaceutical industries. AA-2G production using the CGTase from Paenibacillus macerans was studied, where β-CD, a cheaper substitute, was used as the glycosyl donor. By optimizing the conditions for AA-2G production by P. macerans CGTase using L-ascorbic acid and β-CD as substrates, the highest level of production reported was 13.5 g/L.

Evidence assessment: All findings in this domain are at the in vitro or process-chemistry level. No human trials have evaluated the health effects of AA-2G produced specifically by P. macerans CGTase.

5.6 Plant Growth Promotion and Nitrogen Fixation (Agricultural/Environmental)

Within the genus Paenibacillus, 16 species are considered to harbor nitrogen-fixing strains: P. polymyxa, P. macerans, P. peoriae, P. durus, P. brasilensis, P. graminis, P. odorifer, P. borealis, P. wynnii, P. massiliensis, P. sabinae, P. donghaensis, P. zanthoxyli, P. forsythiae, P. riograndensis, and P. sonchi. Besides the capability to fix nitrogen, many strains belonging to these species present other characteristics important for plant health and growth promotion.

In addition, consortia prepared from different combinations of four bacterial strains, including Paenibacillus macerans, accelerated the phytoextraction of metals from fly ash in Brassica juncea.

Evidence assessment: The plant-growth promotion and nitrogen-fixation literature for P. macerans is scientifically documented at the laboratory and controlled field study levels. This is a well-supported area of the organism's biology, but it is not directly relevant to human health supplementation.

6. Body Systems and Health Areas Associated with P. macerans

In the context of scientific investigation and potential product relevance (rather than established clinical use), P. macerans has been associated with or investigated for activity in the following domains:

Integumentary system (skin): EPS preparations have been assessed for skin hydration and moisturizing properties in pilot in vivo measurements.
Antimicrobial defense: Biosurfactants with demonstrated in vitro activity against pathogenic bacteria and fungi.
Antioxidant pathways: EPS fractions have shown antioxidant activity in in vitro biochemical assays.
Pharmaceutical delivery systems: The CGTase enzyme is a key tool in producing cyclodextrin encapsulation agents that improve bioavailability of drugs and nutraceuticals.
Immune/anti-tumour (genus level, in vitro only): In addition to agricultural applications, Paenibacillus produces a diversity of antimicrobials, enzymes, and exopolysaccharides with relevance in medicine, process manufacturing, and bioremediation, some of which have already been commercialized.

No direct evidence from human clinical trials exists establishing any body system benefit for P. macerans as an oral supplement.

7. Dosage Forms and Reported Dosages

Paenibacillus macerans has not been studied in standardized human dosage trials as a supplement or probiotic. The following production parameters and concentrations have been reported in research settings only:

P. macerans TKU029 produces EPSs at 3.46 g/L and a biosurfactant at 1.78 g/L when grown in media with 2% squid pen powder as the sole carbon/nitrogen source.
In a fermentation study optimizing recombinant CGTase production in E. coli, optimal conditions used 10.0 g/L glycerol, 20.0 g/L tryptone, and 10.0 g/L yeast extract at an initial pH of 7.0, with an IPTG concentration of 0.1 mM and induction at 28 °C for 10 hours. The resulting CGTase activity reached up to 36.4 U/L, and in an up-scaled 500-L fermentor, a CGTase activity of 45.2 U/L was achieved.
By optimizing conditions for AA-2G production by P. macerans CGTase using L-ascorbic acid and β-CD as substrates, the highest level of production reported was 13.5 g/L.
In anaerobic glycerol fermentation studies, strain P. macerans N234A grew fermentatively on glycerol at a maximum specific growth rate of 0.40 h⁻¹.

No human-relevant dosage forms, tablet or capsule dosages, or established supplemental dose ranges have been established or published in peer-reviewed or regulatory literature for P. macerans as a dietary supplement.

8. Safety Considerations and Interactions

8.1 EFSA Qualified Presumption of Safety (QPS) Status

Paenibacillus macerans is not recommended for the EFSA Qualified Presumption of Safety (QPS) list, as determined by the EFSA Panel on Biological Hazards (BIOHAZ), which is responsible for delivering scientific opinions on the maintenance of the list of QPS biological agents intentionally added to food or feed. This is a significant regulatory finding: the QPS status provides a presumption of safety for microorganisms used intentionally in the food chain, and P. macerans does not meet this standard under EFSA's evaluation framework.

8.2 Histamine Production as a Food Safety Hazard

The histamine activity of Bacillus macerans, isolated from Italian cheese during seasoning, has been formally described in the scientific literature. Histamine formation was detected at all temperatures studied (43, 37, 30, 22, and 4°C). The maximum histamine formation was detected at 30°C, with 4285 μg of histamine per mL of quantification broth. Bacillus macerans has been identified as one of numerous histamine-producing strains in the food science literature.

The bacterium is not normally pathogenic in humans, but could cause allergies as a result of its histamine-producing properties. Histamine intoxication from food typically presents as a syndrome including flushing, headache, hypotension, and gastrointestinal symptoms.

8.3 Opportunistic Infection Potential

While Paenibacillus macerans is a bacterium that can be associated with human infections, such infections are rare. Clinically, it has been isolated from wound infections, respiratory tract infections, and other medical conditions, particularly in immunocompromised individuals. The clinical significance of P. macerans mainly lies in its potential to cause opportunistic infections, but it is not typically considered a major pathogen. It may also be involved in nosocomial (hospital-acquired) infections, particularly in patients with underlying conditions or those with prolonged hospital stays.

The genus Paenibacillus includes Gram-positive bacteria that are rarely known to cause infection in humans. A published case report described recurrent Paenibacillus macerans infection in an otherwise healthy 66-year-old man following environmental exposure decades prior. Despite numerous attempts at surgical debridement, Paenibacillus was repeatedly cultured from the soft tissue of the lower extremity wound site over a period of years. Post-operative antibiotic treatment prevented recurrence; however, upon antibiotic discontinuation, Paenibacillus was again cultured from the wound. After multiple rounds of debridement and antibiotic therapy, the patient was started on indefinite, low-dose trimethoprim-sulfamethoxazole therapy to suppress infection resulting from transition of Paenibacillus spores to vegetative cells.

The working hypothesis in this case was that remote childhood trauma resulted in soft tissue inoculation of P. macerans spores, which remained dormant over five decades until reverting to active infection following an elective orthopedic procedure. Several conditions may have contributed to the development of active Paenibacillus infection several decades after initial exposure, including West Nile Virus encephalitis, diabetes mellitus, or the stress of elective ankle surgery.

P. macerans does form ellipsoidal, terminal, or subterminal spores which may last in the soil for many years, and has been identified in blood cultures of infants with infection. Spores of Bacillus-related organisms are resistant to heat, cold, and common disinfectants, allowing them to survive on environmental surfaces for prolonged periods.

8.4 Antibiotic Susceptibility

Antibiotic susceptibility testing of intraoperative tissue culture from a documented clinical case identified TMP-SMX-susceptible P. macerans; the patient treated with 360 mg oral TMP-SMX twice daily remained afebrile and clinically stable. No specific clinical breakpoints have been established for Paenibacillus spp., necessitating the use of nonspecies-related clinical breakpoints.

8.5 Absence of Safety Data for Oral Supplementation

No published toxicology studies, GRAS (Generally Recognized as Safe) determinations, or formal safety evaluations of P. macerans as an orally administered dietary supplement for human use have been identified in the peer-reviewed scientific or regulatory literature. The EFSA QPS exclusion (see Section 8.1) represents the most authoritative regulatory assessment relevant to intentional food-chain use of this organism.

9. Summary of Evidence Strength

The following table summarizes the level of available evidence for areas in which P. macerans has been investigated:

Cyclodextrin / CGTase production: Well-established biochemical and industrial evidence; historically important; no direct human health application of the organism itself.
Skin hydration (EPS): Preliminary; limited to a single strain (TKU029) in pilot in vivo skin measurements. Not a controlled clinical trial.
Antimicrobial (biosurfactant): In vitro laboratory evidence only. No human data.
Antioxidant (EPS): In vitro biochemical assays only. No human data.
Nitrogen fixation / plant growth: Well-supported at the scientific level; not applicable to human health supplementation.
Oral probiotic or supplemental use in humans: No clinical evidence exists. The organism has not been studied in human dietary supplement trials.
Safety for intentional food/feed use: Excluded from EFSA QPS list; histamine-producing properties documented; rare opportunistic infections in humans documented in case reports.

References

Health Conditions

Health conditions that Paenibacillus macerans may help support.

No conditions available.

Body Systems

Body systems that Paenibacillus macerans may help support.

No body systems available.