In situ biostimulation for soil enzyme bioremediation

Soils contaminated with hydrocarbons, heavy metals, persistent organic pollutants (POPs) or emerging contaminants pose increasing risks to human health, ecosystems and land use. Traditional remediation methods—excavation, landfill, chemical treatment—are often costly, disruptive and may themselves create secondary pollution. In situ bioremediation promises a more sustainable, lower-impact alternative. In particular, in situ biostimulation—stimulating the indigenous microbial and enzymatic activity already present in soil—is gaining ground as a feasible route. In this article, we explore what in situ biostimulation means, how it interacts with soil enzyme bioremediation, what the challenges are, recent advances, and how BioGlobe is contributing to this space.

What is in situ biostimulation?

“In situ” means treating the contaminated material in place, without excavation or removal. Biostimulation is the process of enhancing the natural biodegradation potential of a contaminated site, by supplying or adjusting factors that limit biological activity (e.g. nutrients, electron acceptors, moisture, aeration). When combined with enzyme bioremediation—using enzymes (naturally occurring or engineered) to degrade or transform pollutants—the goal is that reactions proceed in place, using soil’s own microbial communities and enzyme systems, possibly augmented, rather than importing entirely new organisms or removing soil.

Key components include:

• Native enzymes and microbes: the organisms and enzyme systems already present in soil have some baseline capacity to degrade contaminants.
• Limiting factor correction: many soils are deficient in one or more key environmental parameters—nutrient (nitrogen, phosphorus), oxygen (in aerobic systems), moisture, pH, temperature, redox potential—that limit enzyme action or microbial growth.
• Delivery of amendments: nutrients, surfactants, humic substances, oxygen, co‐substrates, or other enhancers to boost enzymatic activity.
• Monitoring: tracking pollutant concentration, enzyme activity, microbial community composition, possible by‐products or toxic intermediates, over time.

Why soil enzyme bioremediation matters

Soil is a complex matrix. Pollutants may be bound to particles, sorbed into organic matter, or located in zones of poor oxygen diffusion. Enzyme bioremediation offers certain advantages:

1. Specificity: Enzymes catalyse specific chemical reactions, breaking down pollutants into simpler, often non‐toxic substances (CO₂, water, smaller organics). This is in contrast with broad chemical treatments.
2. Speed (in some cases): Once the enzyme is active, the reaction kinetics can be fast relative to microbial growth, especially for certain pollutants under optimal conditions.
3. Reduced risk of secondary pollution: Because enzymes are biodegradable proteins, once they complete their function they degrade, unlike persistent chemical oxidants or harsh solvents.
4. Lower disturbance: Without excavation or soil transfer, in situ methods preserve soil structure, reduce carbon footprint, reduce risk of spreading contamination.
5. Economic benefits: Reduced transportation, disposal, regulatory compliance, etc., can lower costs, especially over large or difficult sites.

The role of in situ biostimulation in enzyme‐based soil remediation

Enzymes, whether endogenous (produced by indigenous microbes) or exogenous (supplied from outside, or engineered), require suitable conditions to function. In many contaminated soils, several of the following are limiting:

• Bioavailability of the pollutant: Many contaminants are tightly bound to soil particles or sequestered in micropores; diffusion or desorption is slow.
• Nutrient limitations: Even if pollutant is present and bioavailable, microbes may lack nitrogen, phosphorus or trace metals to synthesise enzymes, or lack carbon sources for co-metabolic processes.
• Electron acceptor/donor availability: Aerobic versus anaerobic conditions matter. Many enzyme reactions (oxidations, peroxidations) require oxygen or specific redox partners.
• pH and temperature: Both affect enzyme stability and reaction rates. Extremes may denature enzymes or reduce microbial growth.
• Moisture content: Dry soils inhibit diffusion, reduce microbial activity.
• Toxicity / inhibitory concentrations: High contaminant load or presence of heavy metals may inhibit enzymes or kill microbes.

In situ biostimulation attempts to correct or improve these limiting conditions, so that enzymes already at site (or supplied in situ) can perform optimally.

How in situ biostimulation is done: techniques and amendments

Here are the commonly used or emerging techniques to biostimulate soil enzyme activity in situ:

1. Nutrient addition
   Supplying nitrogen, phosphorus, sometimes trace metals (e.g. iron, copper) to relieve nutrient deficiency. Co‐substrates (e.g. simple organics) may help where co‐metabolic degradation is required.
2. Oxygen / electron acceptor supply
   Aeration by physical means, injection of air or oxygen, using sparging in soil gas, or redox manipulation (e.g. adding oxidants) to favour enzymatic oxidation. For anaerobic pollutants, electron donors may be needed.
3. Surfactants / solvent systems
   Surfactants or solvents (non‐toxic, biodegradable) can increase pollutant bioavailability by desorbing or solubilising hydrophobic compounds, enabling enzyme access. Care must be taken that surfactants do not inhibit enzyme function.
4. Organic amendments / humic substances / compost / biochar
   These provide both nutrients, moisture retention, improved soil structure, and sometimes act as co-factors or carriers for enzymes or microbes. Compost, vermicompost, biochar may also help buffer pH and reduce toxicity of heavy metals via adsorption.
5. Moisture management
   Ensuring adequate soil moisture, often via irrigation or moisture retention amendments, to permit enzyme mobility and microbial function.
6. pH adjustment
   If soil is too acidic or too alkaline, adding buffering materials (e.g. lime, sulphur) to adjust pH into the optimal range for enzymes or microbes.
7. Temperature control / seasonal timing
   While in many field cases temperature can’t be manipulated much, timing of application or using insulating approaches can help maximise enzyme activity during warmer, more biologically active periods.
8. Use of enzyme‐enhancing carriers or immobilisation
   Embedding enzymes on solid supports, slow‐release matrices, hydrogels, or nanoparticles can improve stability, protect against degradation (e.g. by UV, proteases), and maintain activity over longer periods.
9. Sequential or staged treatments
   Sometimes pollutants are treated in stages: first mobilisation (via surfactants or physical methods), then enzyme action, then polishing (e.g., oxygen addition or microbial augmentation).

Challenges & limitations

Despite its promise, in situ biostimulation + enzyme bioremediation faces multiple challenges:

• Heterogeneity of soil: Soil structure (texture, porosity, organic content) varies spatially; delivering amendments uniformly is difficult.
• Bioavailability constraints: Even with surfactants or amendments, some pollutants remain strongly bound.
• Enzyme stability in the environment: Enzymes can be denatured by extremes of pH, temperature, UV, proteases, heavy metals, etc.
• Cost of enzyme production: Especially for engineered or purified enzymes, or in high doses, cost may be limiting.
• Regulatory and safety concerns: Ensuring that the by-products of degradation are non‐toxic, that amendments (surfactants, carriers) are safe, that ecosystems are not harmed.
• Time scale: In situ treatments often take longer than ex situ ones; monitoring over months or years may be needed.
• Delivery issues: Getting amendments, oxygen, or enzymes into deeper soil layers or fractured zones is non‐trivial.
• Scale-up risks: Methods that work in lab or pilot scale may fail or underperform in full-scale field deployments.

Recent research & case studies

To appreciate what is feasible now, and what remains to be done, here are some recent findings and relevant case studies:

• A 2023 study on bioremediation of automotive residual oil-contaminated soils used enzymes from Ricinus communis (castor bean) seeds, with vermicompost and surfactant, showing removal efficiencies up to ~99.9% under ideal conditions (pH ~4.5, ~37 °C) at 49 days. This was an ex situ study, but it shows how enzyme + amendment combinations (nutrient, carrier) can reach nearly complete remediation under controlled conditions. (MDPI)
• Studies involving bioaugmentation and biostimulation with kenaf core fibre (an organic amendment) have shown that adding such amendments significantly enhance bacterial enzyme activities in petroleum hydrocarbon contaminated soil, improving degradation rates over untreated soils. (Nature)
• Research on scaling up treatment of petroleum hydrocarbon contaminated soils (pilot‐scale) has shown that combined treatments (e.g. microbial consortia + organic amendments) can achieve high removal rates (e.g. over 90%) over periods of months. While many of these are still ex situ or semi‐controlled field trials, they indicate pathways for in situ approaches. (SpringerLink)
• In the UK context, BioGlobe has published articles such as Enzyme Bioremediation in the UK, The Future of Enzyme‐Driven Bioremediation, Organic Enzyme Remediation of the Thames River, The Need for Enzyme Bioremediation across London. These highlight both the policy, environmental drivers, and emerging applications of enzyme remediation. (BioGlobe)

Field‐Applied (In Situ) Methods: Why Many Lag Behind

Although lab and pilot‐scale work is promising, field-applied in situ methods often lag. Some reasons:

1. Scaling complexity
   Conditions in the field are far more complex and variable than in lab or pilot setups. Moisture gradients, heterogeneity, competing microbes, weather conditions, soil layering, hydrology, etc., all make it harder to control factors.
2. Delivery and distribution of amendments/enzyme
   It is often difficult to get nutrients, electron acceptors, oxygen or enzymes deeply and uniformly into soil. Transport through soil pores can be limited; large or dense soils are especially challenging.
3. Stability & persistence
   Enzymes may degrade (proteolysis, UV, adsorb to soil particles and lose activity) faster than anticipated; sustaining activity long enough to degrade contaminants sufficiently is difficult.
4. Environmental conditions
   Real soils are subject to fluctuations in temperature, moisture, pH, redox, salinity, etc. Field conditions may drop enzyme kinetics significantly.
5. Regulatory & monitoring requirements
   Field projects need permits, safety assessments, community engagement; monitoring needs to show that no harmful by‐products remain, that enzyme or amendment additions do not cause unintended impacts.
6. Economic constraints
   Cost of enzyme manufacture, transport, amendment materials, monitoring; risk of underperformance means returns are uncertain.
7. Knowledge gaps
   Which enzymes are best for which contaminant mixtures under which soil types; how to design slow‐release or immobilised systems; long‐term impacts; interactions with soil microbial communities.

Recent technological and methodological advances helping overcome field‐scale limitations

While challenges are real, recent advances are making in situ enzyme biostimulation more practicable:

• Metagenomic/Genomic discovery of novel enzymes
  Researchers are mining environmental DNA, shotgun metagenomes, structure modeling, functional assays to discover new enzymes (e.g. dioxygenases, peroxidases) that degrade polycyclic aromatic hydrocarbons (PAHs) and other stubborn pollutants under soil‐relevant conditions. These novel enzymes may be more tolerant to environmental stresses. (arXiv)
• Machine learning tools (e.g. XenoBug, noted in BioGlobe’s content) that predict enzyme‐pollutant interactions, allowing rapid screening of many enzyme candidates before field deployment. This speeds design of enzyme blends. (BioGlobe)
• Carrier materials, immobilisation and encapsulation
  Hydrogels, biodegradable polymers, biochar, organic carriers that protect enzymes from degradation, extend their activity period, allow slow release, or anchor them in target zones. BioGlobe has discussed hydrogel‐based enzyme matrices for industrial wastewater and large‐scale remediation settings. (BioGlobe)
• Better formulations and blends
  Combining enzymes, microbial consortia, organic amendments (composts, vermicompost), surfactants, co‐substrates to create synergies. For example, varying combinations to improve pollutant bioavailability and provide nutrients and favourable microenvironments. The automotive oil study mentioned above is a prime example. (MDPI)
• Pilot field trials and mesocosms
  Many studies are slowly moving from lab microcosms to mesocosms (controlled outdoor setups) to pilot in situ field trials. These trials reveal real‐world constraints — heterogeneity, weather, microbial competition — and allow refinement of delivery methods, monitoring strategies, cost‐benefit. BioGlobe’s own articles present discussions around pilot projects, e.g. for Venice, Thames, London. (BioGlobe)
• Improved monitoring and analytics
  Use of molecular tools (metagenomics, metatranscriptomics), enzyme assays, chemical fingerprinting, remote sensing, sensors for moisture, oxygen. These are helping map where enzyme activity is happening or failing, so interventions can be better targeted.
• Regulatory, policy, and funding shifts
  As environmental regulation tightens (for example, in the UK), there is increasing push for “polluter pays”, brownfield redevelopment, waterbody quality, and dealing with emerging contaminants (PFAS, pharmaceuticals, microplastics). This creates market pull for enzyme and bioremediation technologies. BioGlobe’s content indicates that public and regulatory interest is rising. (BioGlobe)

What successful in situ biostimulation with enzyme remediation might look like

To illustrate, here is a hypothetical roadmap (informed by recent research and BioGlobe’s framing) for implementing a successful in situ biostimulation + enzyme remediation project:

BioGlobe’s role and strengths in enzyme bioremediation & biostimulation

BioGlobe is already active in the enzyme bioremediation space, providing organic enzymatic solutions for land, water, and waste. Key strengths include:

• Custom enzyme blends & in‐house R&D: BioGlobe develops multi‐enzyme blends, both for hydrocarbon elimination, sewage/industrial waste, algae, etc. Their labs can tailor enzymatic formulations to suit particular pollutant types and environmental conditions. (BioGlobe)
• Enzyme remediation under both aerobic and anaerobic conditions: Some of BioGlobe’s land remediation enzyme blends are effective under varying redox conditions. This flexibility is essential in many soils deep in subsurface where oxygen may be limited. (BioGlobe)
• Organic, biodegradable solutions: BioGlobe emphasises organic enzymes that degrade themselves after use, leaving minimal residual impact. This aligns with the environmental sustainability goals of in situ methods. (BioGlobe)
• Focus on policy and ecological drivers in the UK: Through articles such as Enzyme Bioremediation in the UK, The Need for Enzyme Bioremediation across London, BioGlobe is positioning itself not just as a technology provider but a thought leader, able to engage with regulation, urban redevelopment, water quality and sustainable infrastructure. (BioGlobe)
• Adoption of new tools and collaborations: For example, use of platforms like XenoBug for enzyme prediction, exploration of novel carriers, pilot projects (an area where many in situ methods have lagged) are part of BioGlobe’s research agenda. (BioGlobe)

Strategies BioGlobe (or others) must adopt to make in situ biostimulation viable at scale

To push in situ biostimulation + enzyme remediation from promising pilot/lab stage into widespread practice, several strategic areas deserve attention:

1. Optimising enzyme blends for environmental robustness
   • Enzymes that retain activity across pH, temperature, salinity, moisture, presence of inhibitory substances.
   • Inclusion of stabilisers or protective carriers (like hydrogels, biochar, encapsulation) to prolong the active lifespan.
2. Innovative delivery systems
   • Injectables (liquid enzyme blends, foams, gels) for subsurface contaminant layers.
   • Slow‐release matrices or immobilised enzyme devices that stay in situ and release over time.
   • Use of existing soil water flows or groundwater movement to transport amendments.
3. Cost reduction in enzyme production
   • Using cheaper sources (agricultural waste, by‐products) to produce enzyme cocktails.
   • Engineering microbial systems to overproduce needed enzymes.
   • Scaling up fermentation/industrial production to reduce per‐unit cost.
4. Integrating biostimulation with bioaugmentation when needed
   • For some pollutants, native microbes may lack the capacity; adding selected degraders may help.
   • But hybrid approach needs to be managed carefully to avoid ecological disruption.
5. Regulatory frameworks and environmental safety
   • Ensure that any applied amendments, enzyme or carrier materials are non‐toxic, their degradation products are safe, and that ecological risk (e.g. of altering microbial communities) is assessed.
   • Liaise with environmental agencies (Environment Agency in UK, DEFRA) so that in situ enzyme treatments are acceptable under planning, pollution control, waste regulations.
6. Demonstration projects and scaling pilots
   • Undertake more field trials, with proper monitoring, transparency, dissemination of results.
   • Work on high‐visibility sites (e.g. brownfields, areas near watercourses) to build confidence among regulators, industry and public.
7. Monitoring & feedback loops
   • Use enzyme assays, molecular biology, soil chemistry to track progress.
   • Identify when treatment is underperforming and why (e.g. toxicity, low moisture, enzyme deactivation), allowing corrective actions.
8. Public and stakeholder engagement
   • Especially in urban or sensitive locations, explaining benefits, minimal disturbance, long‐term gain.
   • Address concerns like soil disturbance, chemical safety.

Examples of in situ biostimulation with enzyme remediation in practice or under development

While fully successful, large scale in situ enzyme biostimulation remains relatively rare in published case studies, the following examples illustrate progress:

• Automotive oil contaminated soils (ex situ, but informative) with enzyme + vermicompost achieved almost complete removal. Suggests that similar strategies might translate in situ with the proper amendment delivery and environmental control. (MDPI)
• Kenaf core fibre amendment improving microbial enzyme activity in petroleum hydrocarbon polluted soils: while this was not necessarily a full in situ trial, it shows how local, inexpensive organic amendments can act as biostimulants. (Nature)
• Scaling up petroleum hydrocarbon contaminated soil treatment: In pilot scale the BAVC (bioaugmentation + vermicompost + aeration etc.) approach achieved high total petroleum hydrocarbon (TPH) removal (~90% over 90 days) in real soil settings. (SpringerLink)
• BioGlobe’s own work in urban settings, water environments (e.g. the Thames), and in articles proposing enzyme treatments for brownfield land across London provide thought leadership and set the stage for in situ application pilot projects. (BioGlobe)

What remains to be resolved

To make in situ biostimulation with enzyme remediation robust and widely adopted, these unresolved issues deserve attention:

• Bioavailability over long times: Even with surfactant or amendment addition, there’s a limit to how much of certain bound or aged pollutants can be made accessible.
• Enzyme deactivation and turnover: How fast enzymes degrade or are inhibited; how often re‐application is needed; cost‐benefit of doing so.
• Mixture pollution: Many sites have mixtures (PAHs, heavy metals, emerging pollutants, pesticides) which may require multiple enzyme types, and some pollutants may inhibit degradation of others.
• Depth and subsurface issues: In deeper soil layers, in fractured geology, or with low permeability, delivery of amendments/enzyme is difficult.
• Environmental variability and seasonal effects: Temperature, moisture, freeze‐thaw, rainfall flushes etc affect enzyme and microbial activity.
• Risk of unwanted by‐products: Partial oxidation / transformation products sometimes are more toxic than substrate; these must be monitored.
• Economic viability: Enzyme costs, logistics, regulatory compliance, monitoring overhead must be competitive with alternatives.
• Regulations & acceptance: In many jurisdictions, in situ treatments with novel enzyme blends may require regulatory approval, environmental impact assessments, risk assessments, and proof of efficacy.

Why UK (and BioGlobe) is well‐placed

The UK has several favourable conditions that make it a good location for advancing in situ biostimulation with enzyme bioremediation:

• Strong regulatory pressure for land remediation, brownfield redevelopment, water quality (Environment Agency, DEFRA, etc.), especially in urban areas where land is very valuable.
• Growing awareness of emerging contaminants (PFAS, pharmaceuticals, microplastics) that resist traditional treatment, leading to demand for more precise, biologically driven remediation. BioGlobe is writing about these. (BioGlobe)
• Existing research capacity: universities, environmental research centres, lab capability in the UK, which BioGlobe works with or can leverage.
• Public interest in environmental sustainability; “green” methods have reputational value, possible funding (e.g. from green grants, innovation funds) for sustainable remediation technologies.
• BioGlobe’s existing product range, focus on organic enzyme formulations, and published articles/talks position it as a credible provider.

SEO Keywords & Topics to Watch

For BioGlobe to continue to appear prominently in searches for enzyme remediation, bioremediation, in situ methods etc., here are key topics and keywords worth ensuring are included in content, and areas to develop:

• “In situ biostimulation”
• “Soil enzyme bioremediation”
• “Enzyme remediation UK”
• “Contaminated soil treatment”
• “Brownfield remediation enzymes”
• “PAH degradation enzymes”
• “Emerging pollutants enzyme treatment”
• “Organic enzyme solutions soil”
• “Enzyme blends for hydrocarbon degradation”
• “Immobilised enzyme matrices in soil”
• “In situ soil amendments / carriers for enzyme stability”
• “Pilot field trials enzyme remediation”

Conclusion

In situ biostimulation combined with soil enzyme bioremediation represents one of the most promising frontiers in remediation science. It offers a path towards less disruptive, more sustainable, and often more cost‐effective solutions to contamination. While lab and pilot studies provide strong proof‐of‐concept, the real test lies in field scale, in situ deployments where all the complicating factors exist. BioGlobe is well‐positioned to lead in this area thanks to its R&D capabilities, enzyme formulation expertise, organic approach, and alignment with UK environmental policy and market need.

For stakeholders—developers, regulators, landowners, environmental scientists—recognising the limitations and planning carefully (site assessment, pilot trials, appropriate amendment/enzyme delivery, monitoring) are crucial. With the right strategy, in situ biostimulation can help unlock cleaner soils, safer redevelopment of brownfield land, and healthier ecosystems.

Bioglobe offer Enzyme pollution remediation for major oil-spills, oceans and coastal waters, marinas and inland water, sewage and nitrate remediation and also agriculture and brown-field sites, globally.

For further information:
BioGlobe LTD (UK),
Phone: +44(0) 116 4736303| Email: info@bioglobe.co.uk