Photobacterium lipolyticum

Photobacterium lipolyticum: A Scientific Reference

Preface: Status as a "Dietary Supplement" or "Natural Ingredient"

A thorough search of peer-reviewed literature (PubMed/PMC, Web of Science), government health databases (NIH, EFSA, WHO, NCCIH), official pharmacopeias, and reputable evidence-synthesis databases reveals no evidence that Photobacterium lipolyticum is recognized, regulated, sold, or studied as a dietary supplement or functional food ingredient in any jurisdiction. It does not appear in the NIH Office of Dietary Supplements fact sheets, the EFSA register of authorized novel foods, GRAS notices issued by the FDA, the WHO monographs on selected medicinal plants, ESCOP monographs, or German Commission E monographs. It is absent from Examine.com's ingredient database and from Cochrane systematic reviews.

The organism is exclusively studied within the fields of marine microbiology, extremophile biochemistry, industrial enzymology, and biofuel research. The article below therefore covers all verified scientific knowledge about this organism in full, sourced exclusively from primary research and authoritative taxonomic databases. The complete absence of traditional medicinal use and the complete absence of human clinical evidence are stated plainly and explicitly throughout.

Identity and Nomenclature

Formal Taxonomic Name and Etymology

Photobacterium lipolyticum was formally named by Yoon, Lee, Kim, and Oh in their 2005 publication, "Photobacterium lipolyticum sp. nov., a bacterium with lipolytic activity isolated from the Yellow Sea in Korea," published in the International Journal of Systematic and Evolutionary Microbiology, volume 55, pages 335–339.

The specific epithet lipolyticum is derived from the Greek lipos, meaning animal fat, lard, or tallow, and the Greek adjective lytikon, meaning "able to dissolve," giving the Neo-Latin adjective lipolyticum the meaning "dissolving fat or lipid." This name reflects the organism's defining biochemical property: its robust lipolytic (fat-hydrolyzing) enzymatic activity.

Taxonomic Classification

The genus Photobacterium comprises Gram-negative, oxidase-positive and catalase-positive bacteria in the family Vibrionaceae. Photobacterium is a genus of facultatively aerobic gammaproteobacteria whose members are found in various niches, such as the guts, surface, or light organs of fish, free-living throughout the marine water column, and inside decaying animal tissue.

The full classification of Photobacterium lipolyticum is:

• Domain: Bacteria
• Phylum: Proteobacteria
• Class: Gammaproteobacteria
• Order: Vibrionales
• Family: Vibrionaceae
• Genus: Photobacterium
• Species: Photobacterium lipolyticum

The nomenclatural status of the name is "validly published under the ICNP." Under the German risk classification system, imported in 2023, Photobacterium lipolyticum is assigned to risk group 1, the lowest category.

Type Strain

The type strain, designated M37T, is a Gram-negative, motile, non-spore-forming, pleomorphic, and lipolytic bacterial strain, isolated from an intertidal sediment of the Yellow Sea in Korea. On the basis of phenotypic properties and phylogenetic and genomic distinctiveness, strain M37T (=KCTC 10562BPT=DSM 16190T) was placed in the genus Photobacterium as a novel species.

Natural Source and Habitat

Isolation and Ecology

The type strain M37, showing lipolytic activity, was isolated from an intertidal flat of the Yellow Sea in Korea and identified as Photobacterium lipolyticum sp. nov. The Yellow Sea (also known as the West Sea) is a semi-enclosed marginal sea of the Pacific Ocean lying between China and the Korean Peninsula, characterized by tidal flats with cold, shallow coastal sediments — an environment that places strong selective pressure on organisms to produce cold-active enzymes.

The organism grows optimally at 25–28 °C and in the presence of 1–2% NaCl. It does not grow without NaCl or in the presence of more than 6% NaCl, confirming its marine obligate halophily.

The habitats and isolation sources of Photobacterium species in general include seawater, sea sediments, saline lake waters, and a variety of marine organisms with which photobacteria establish different relationships, from symbiosis to pathogenic interactions.

Ecological Roles of the Genus

Members of the genus Photobacterium are considered a special group of bacteria because some species are capable of producing essential polyunsaturated fatty acids, antibacterial compounds, lipases, esterases, and asparaginases. They are also used as biosensors in food and environmental monitoring and as detectors of drowned victims, as well as being important symbionts.

Several species of this genus contain bioluminescent strains in symbiosis with marine fish and cephalopods; in addition, other species enhance growth at pressures above 1 atmosphere by means of several high-pressure adaptation mechanisms.

With respect to P. lipolyticum specifically, members of this genus, specifically Photobacterium lipolyticum, have been identified in the herbivorous sea urchin Paracentrotus lividus. Lysates of lipolytic enzymes produced by such bacteria are thought to nutritionally benefit the sea urchin as a host, and a lipolytic role beneficial for the sea urchin is inferred from a phylotype closely related to the anaerobic, lipolytic Photobacterium lipolyticum (Yoon et al. 2005).

Chemotaxonomic Fingerprint

Strain M37T is characterized chemotaxonomically by having Q-8 as the predominant respiratory lipoquinone and C16:1 ω7c and/or iso-C15:0 2-OH and C16:0 as the major fatty acids. The DNA G+C content is 47 mol%.

Phylogenetic analyses based on 16S rRNA gene sequences placed strain M37T within the clade comprising Photobacterium species, forming a coherent cluster with the type strains of Photobacterium profundum and Photobacterium indicum, with 16S rRNA gene similarity levels of 97.5–98.0%. Similarities between 16S rRNA gene sequences of strain M37T and those of the type strains of the other Photobacterium species ranged from 93.9% (with Photobacterium fischeri) to 96.2% (with Photobacterium phosphoreum).

Traditional and Historical Use

No traditional or historical use of Photobacterium lipolyticum — or of preparations derived from it — has been documented in any culture, time period, or medical tradition. The organism was not described or formally named until 2005, following modern microbiological isolation and sequencing techniques. The intertidal marine sediment from which it was isolated has no documented ethnobiological tradition of medicinal use involving this specific bacterium, and no herbal, Ayurvedic, Traditional Chinese Medicine, indigenous, or Western herbal medicine tradition references this organism or its enzyme products. The entirety of the scientific literature on this species is post-2005 and is confined to biotechnology, industrial enzymology, and marine microbial ecology.

Key Biochemical Constituents and Active Compounds

Lipase M37: The Primary Characterized Enzyme

The scientifically defining compound produced by Photobacterium lipolyticum is Lipase M37 (also written LipM37), a cold-active triacylglycerol lipase of exceptional interest to industrial biotechnology. The corresponding gene was cloned using the shotgun method. The amino acid sequence deduced from the nucleotide sequence (1,023 bp) corresponded to a protein of 340 amino acid residues with a molecular weight of 38,026 Da.

No sequence similarity was found with any known bacterial lipases or esterases; instead, the most similar enzymes were several filamentous fungal lipases. Although the similarity was very low (less than 16%), there were many conserved regions over the entire sequence and the N-terminal oxyanion hole (RG) region, a signature sequence of filamentous fungal lipases.

Lipase M37 has a high lysine content (9.7%) in its protein sequence. Most lysine residues are located evenly over the surface of the protein, except for the lid structure region, which makes cross-linked enzyme aggregate (CLEA) preparation yield quite high (~93%).

Catalytic Properties and Cold Adaptation

The M37 lipase shows an extremely low activation energy and strong activity at low temperatures, with optimum activity seen at 298 K (25 °C) and more than 75% of the optimum activity retained down to 278 K (5 °C). Although the M37 lipase is most closely related to the filamentous fungal lipase Rhizomucor miehei lipase (RML) at the primary structure level, their activity characteristics are completely different.

The M37 lipase displayed a maximum activity at 25 °C and maintained its activity at a low temperature range (5–25 °C) with an activation energy (E_a) of 2.07 kcal/mol.

M37 exhibits a low activation energy towards triglyceride substrates, stability in non-aqueous solvents, and catalytic activity at low temperatures, due to its apparent ability to function at low temperatures (psychrophilicity). Some unique structural features of M37 are thought to underlie these properties.

Structural Basis of Cold Adaptation

In an effort to identify structural components of cold adaptation in lipases, researchers determined the crystal structure of the M37 lipase at 2.2 Å resolution and compared it to that of non-adapted RML. Structural analysis revealed that M37 lipase adopted a folding pattern similar to that observed for other lipase structures. However, comparison with RML revealed that the region beneath the lid of the M37 lipase included a significant and unique cavity that would be occupied by a lid helix upon substrate binding.

In addition, the oxyanion hole was much wider in M37 lipase than in RML. These distinct structural characteristics of M37 lipase are proposed to facilitate the lateral movement of the helical lid and subsequent substrate hydrolysis, which might explain its low activation energy and high activity at low temperatures.

Structural studies of the M37 lipase from Photobacterium lipolyticum revealed several features of cold-adapted lipases. Their structures are believed to be flexible, loose, and maintained by a relatively small number of weak intramolecular bonds. These structural assets explain the enhanced lability of cold-active enzymes. The current understanding is that their increased flexibility allows psychrophilic enzymes to be active at low temperatures.

Interfacial Activation Mechanism

The protein contains a so-called amphipathic lid region that covers the catalytic residues of the active site, in addition to an α-helical "flap" region. It is thought that the lid and flap regions determine interfacial activation of M37. All lipases identified to date share a typical α/β hydrolase fold and a catalytic triad composed of Ser, His, and Asp at the active site.

Optimum pH and Substrate Specificity

The CLEA form of M37 evidences an optimal temperature of 30 °C and an optimal pH of 9–10. However, under specific reactor conditions for DEM (diethyl malate) hydrolysis, the optimum temperature and pH conditions were found to be 50 °C and pH 4.0, respectively, revealing that M37 can function as a uniquely acidic lipase, stably carrying out DEM hydrolysis at acidic pH for extended periods.

Methanol Tolerance

Photobacterium lipolyticum lipase (M37) was determined to be quite stable in a medium containing a high concentration of methanol. The enzyme activity was maintained for longer than 48 h without any loss at a methanol concentration of 10%. This property distinguishes M37 from many commercially used lipases and makes it attractive for biodiesel catalysis.

Polyunsaturated Fatty Acid Production in the Genus

While not specifically documented for P. lipolyticum, the broader Photobacterium genus is notable for PUFA biosynthesis. These bacteria exhibit optimal growth at temperatures between 18–25 °C and include psychrophilic species capable of producing polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA). Marine bacteria, particularly the genus Photobacterium, Shewanella, Colwellia, Moritella, Psychromonas, Vibrio, and Alteromonas, are found to be among the major microbial producers of polyunsaturated fatty acids. These species are the only ones known to produce the long-chain polyunsaturated fatty acid (PUFA) eicosapentaenoic acid (EPA). These PUFA-producing capacities are specifically attributed to related species such as P. profundum, not unambiguously to P. lipolyticum itself based on current literature.

Scientific Evidence by Area of Research Interest

Important qualification: All scientific evidence presented below is confined to in vitro biochemistry, laboratory enzyme characterization, and industrial biotechnology research. There are no human clinical trials, no animal feeding studies for health outcomes, no randomized controlled trials, no systematic reviews, and no observational epidemiological studies of Photobacterium lipolyticum or its lipase M37 in the context of human or animal health, dietary supplementation, or disease treatment. All evidence is preliminary biochemical characterization, rated as the weakest possible tier of evidence for health claims.

1. Industrial Biocatalysis and Enzymatic Hydrolysis (In Vitro Evidence Only)

Lipase is an industrially useful enzyme catalyst because it can hydrolyze triglycerides with various fatty acid chains. It can also catalyze various ester syntheses or transesterification in non-aqueous systems.

The primary research application for M37 lipase is in biodiesel production. In biodiesel production, the M37 lipase showed a similar or superior conversion yield to Novozym435 (the industry standard, Candida antarctica lipase B) in 3-stepwise methanol feeding. The M37 lipase evidenced significantly higher conversion yields in the 2- and 1-step methanol feeding reactions. Particularly in the 1-step process using 10% methanol where almost no conversion was detected by Novozym435, the biodiesel yield achieved with M37 lipase reached a level of up to 70% of the possible maximum yield.

These results are in vitro biotechnology findings of industrial relevance and have no established relevance to human health.

2. Cross-Linked Enzyme Aggregate (CLEA) Technology (In Vitro Evidence Only)

Methanol-tolerant lipase M37 from Photobacterium lipolyticum was immobilized using the cross-linked enzyme aggregate (CLEA) method. Lipase M37 has a high lysine content (9.7%) in its protein sequence. Most lysine residues are located evenly over the surface of the protein, except for the lid structure region, which makes the CLEA preparation yield quite high (~93%). CLEA M37 evidences an optimal temperature of 30 °C, and an optimal pH of 9–10.

3. Polyhydroxybutyrate (PHB) Granule Immobilization (In Vitro Evidence Only)

Photobacterium lipolyticum M37 lipase (LipM37) was immobilized on the surface of intracellular polyhydroxybutyrate (PHB) granules in Escherichia coli. LipM37 was genetically fused to Cupriavidus necator PHA synthase (PhaC_Cn), and the engineered PHB operon containing the lipM37-phaC_Cn gene successfully mediated the accumulation of PHB granules (85 wt.%) inside E. coli cells. The immobilized LipM37 was comparable with the free form of LipM37 except for a favorable increase in thermostability.

The immobilized LipM37 was used to synthesize oleic acid methyl ester (biodiesel) and oleic acid dodecyl ester (wax ester), and yielded 98.0% conversion in esterification of oleic acid and dodecanol.

4. Fine Chemical Synthesis (In Vitro Evidence Only)

It was found that M37 showed the lowest p-nitrophenyl caproate (PNPC) hydrolysis activity but the highest DEM (diethyl malate) hydrolysis activity among the four laboratory lipases tested. P. lipolyticum M37 could selectively produce 4-ethyl malate (4-EM), a raw material for photoresist, by position-specifically degrading DEM. The optimum temperature and pH conditions for the M37 reaction in this application were found to be 50 °C and pH 4.0, respectively, using a reactor system.

Overall Assessment of Evidence Strength

All evidence for Photobacterium lipolyticum and its products is exclusively in vitro biochemical characterization. There is no evidence from cell culture models of human disease, no animal model research relating to health outcomes, and no human trials of any design. Evidence strength for any health-related claim would be rated at the lowest possible level — well below even the "insufficient evidence" rating used by bodies such as NCCIH or the Natural Medicines database. No health claims of any kind are supported by the peer-reviewed literature.

Body Systems and Health Areas: Status of Research

Photobacterium lipolyticum has not been studied in relation to any human body system or health area in a clinical or preclinical health-outcome context. The following notes its potential relevance to basic science areas, not clinical ones:

• Lipid metabolism (theoretical/in vitro only): The lipase M37 hydrolyzes triacylglycerols and medium-chain fatty acid esters in vitro. No studies have examined any effect on dietary lipid digestion, fat absorption, dyslipidemia, or metabolic syndrome in any organism.
• Marine microbiome (descriptive ecology only): Photobacteria, including Photobacterium lipolyticum, have been identified in the gut digesta and fecal pellets of marine invertebrates such as the sea urchin Paracentrotus lividus. The relevance of this finding to human gut health or the human microbiome has not been investigated.
• Omega-3/PUFA research (genus-level only): Polyunsaturated fatty acids (PUFAs) play an important role in human diet. Despite the wide-ranging importance and benefits from heart health to brain functions, humans and mammals cannot synthesize PUFAs de novo. While the Photobacterium genus is recognized as a potential microbial source of EPA, no PUFA production has been specifically documented for P. lipolyticum itself, and no clinical research exists in this context.

Dosage Forms and Dosages

No dosage forms or dosage regimens exist for Photobacterium lipolyticum as a supplement or therapeutic agent. The organism and its lipase M37 have not been formulated into any supplement, pharmaceutical, probiotic, or functional food product described in the peer-reviewed literature. Research preparations used in biotechnology studies are expressed as units of enzyme activity (U/g or U/mg protein) or as concentrations of purified recombinant protein produced in Escherichia coli expression systems. These are not dosage forms relevant to human administration.

Safety Considerations

Regulatory Risk Classification

The nomenclatural status of Photobacterium lipolyticum is "validly published under the ICNP." Under the German risk classification system (imported in 2023), the species is assigned to risk group 1, the lowest biosafety tier, indicating it is not considered a hazard to healthy individuals under normal conditions of work.

In contrast, the genus-level classification for Photobacterium in Canada is risk group 2, with a containment level of 2, though the animal classification remains risk group 1. The disparity reflects the fact that some Photobacterium species — notably Photobacterium damselae — are pathogenic to aquatic animals and occasionally to humans.

Pathogenicity in the Genus

Some Photobacterium strains are pathogenic for aquatic animals and can therefore indirectly affect human health through their consumption, such as Photobacterium damselae subsp. However, P. lipolyticum specifically has not been reported as a human pathogen in any peer-reviewed literature. Its assignment to risk group 1 (Germany) is consistent with a non-pathogenic status in healthy individuals.

Halophily and Growth Requirements

The type strain is a Gram-negative, motile, non-spore-forming, pleomorphic and lipolytic bacterium that grows optimally at 25–28 °C and in the presence of 1–2% NaCl. It does not grow without NaCl or in the presence of more than 6% NaCl. These strict growth requirements mean the organism cannot grow in typical human physiological conditions (which offer 0.9% NaCl in isotonic fluid) at body temperature (37 °C), providing a biologically plausible barrier to infection.

Interactions and Contraindications

No drug–bacterium interactions, supplement–bacterium interactions, or contraindications for Photobacterium lipolyticum have been described in the scientific literature, as the organism has not been studied in any medicinal or nutritional context. No toxicology studies (acute, subacute, or chronic), genotoxicity assays, allergenicity assessments, or regulatory safety dossiers have been published for this organism.

Recombinant Enzyme Preparations: Industrial Context

Research use of M37 lipase has involved its recombinant expression in E. coli. The novel protein M37 was produced in both a soluble and insoluble form when the E. coli cells harboring the gene were cultured at 18 °C. Any industrial enzyme preparation derived from this source would be subject to normal food enzyme safety assessment regulations (e.g., EFSA guidance on food enzymes), but no such dossier has been submitted or made publicly available as of the time of writing.

Summary of Verified Knowledge

• Organism type: Marine, Gram-negative, facultatively aerobic gammaproteobacterium in the family Vibrionaceae.
• Discovery: Formally described in 2005 from intertidal sediment of the Yellow Sea, Korea.
• Principal compound of interest: Lipase M37 — a cold-active, methanol-tolerant, 340-amino-acid triacylglycerol lipase with unique structural and catalytic properties.
• Research domain: Exclusively industrial biotechnology (biodiesel, fine chemicals, enzyme engineering) and marine microbiology.
• Traditional use: None documented.
• Human clinical evidence: None. Not a single human or animal health study exists.
• Supplement status: Not recognized by any regulatory body as a supplement, novel food, GRAS substance, or medicinal ingredient.
• Biosafety: Risk group 1 (Germany, species level); non-pathogenic for healthy humans based on available evidence.

References

• LPSN (List of Prokaryotic names with Standing in Nomenclature) — Photobacterium lipolyticum species entry, DSMZ
• Yoon JH, Lee JK, Kim YO, Oh TK (2005). Photobacterium lipolyticum sp. nov., a bacterium with lipolytic activity isolated from the Yellow Sea in Korea. Int J Syst Evol Microbiol 55:335–339. Microbiology Society.
• Yoon et al. (2005). Photobacterium lipolyticum sp. nov. — PubMed abstract (PMID 15653897)
• Ryu HS, Kim HK, Choi WC, et al. (2006). New cold-adapted lipase from Photobacterium lipolyticum sp. nov. that is closely related to filamentous fungal lipases. Appl Microbiol Biotechnol 70(3):321–326. PubMed PMID 16088345.
• Ryu et al. (2006). New cold-adapted lipase from Photobacterium lipolyticum sp. nov. Applied Microbiology and Biotechnology. Springer Nature.
• Jung SK, Jeong DG, Lee MS, et al. (2008). Structural basis for the cold adaptation of psychrophilic M37 lipase from Photobacterium lipolyticum. PubMed PMID 18186467.
• Yang JK, et al. (2009). Catalytic properties of a lipase from Photobacterium lipolyticum for biodiesel production containing a high methanol concentration. Journal of Biotechnology. ScienceDirect.
• Yang JK et al. (2009). Catalytic properties of a lipase from Photobacterium lipolyticum for biodiesel production. PubMed PMID 19447334.
• Kim HK et al. (2015). In Situ Immobilized Lipase on the Surface of Intracellular Polyhydroxybutyrate Granules. Applied Biochemistry and Biotechnology. Springer Nature.
• Production of 4-Ethyl Malate through Position-Specific Hydrolysis of Photobacterium lipolyticum M37 Lipase. PMC9628889.
• Périgny et al. (2013). Purification, characterization and preliminary X-ray diffraction analysis of a cold-active lipase (CpsLip) from the psychrophilic bacterium Colwellia psychrerythraea 34H. PMC3729175.
• Revisiting the genus Photobacterium: Taxonomy, ecology and pathogenesis. ResearchGate (2017).
• Polyunsaturated fatty acids in marine bacteria and strategies to enhance their production. Applied Microbiology and Biotechnology (2018). Springer Nature.
• Allemann MN, Shulse CN, Allen EE (2019). Linkage of Marine Bacterial Polyunsaturated Fatty Acid and Long-Chain Hydrocarbon Biosynthesis. PMC6463001.
• Frontiers in Microbiology (2023). Advances in cold-adapted enzymes derived from microorganisms.
• LPSN — Genus Photobacterium entry (risk group classifications). DSMZ.
• Interfacial activation of M37 lipase: A multi-scale simulation study. ResearchGate.