Scanning agro-industrial wastes as substrates for fungal biopesticide production: Use of Beauveria bassiana and Trichoderma harzianum in solid-state fermentation

Optimization of Metarhizium koreanum MN031-Mt 46: Nutritional Supplementation to Improve Conidia and Cuticle-Degrading Enzyme Production by Solid-State Fermentation

This study aimed to evaluate five different mixed agricultural wastes as potential substrates for solid-state fermentation (SSF) to produce conidia of Metarhizium koreanum MN031-Mt 46. Single-factor experiments and a Box-Behnken design (BBD) were employed to optimize the fermentation conditions for enhanced conidia yield. Results indicated that a mixed substrate comprising broken rice and rice bran significantly enhanced the optimal production of aerial conidia of MN031-Mt 46. Optimal fermentation conditions established through response surface methodology (RSM) revealed that with the addition of shrimp shell waste to the mixed substrate, conidia production increased to 8.45 × 108 conidia per gram of dry substrate at 26.19°C temperature, 39.76% moisture, and 1.45% of shrimp shell waste after 301.87 h of incubation. Enhanced conidia performance indices were observed, including higher conidia weight, increased water content, and reduced residue post-harvest. The optimized fermentation conditions resulted in enhanced cuticle-degrading enzymatic activities, with maximum activities of 58.78 ± 2.29 U g-1 ds for protease, 126.57 ± 6.47 U g-1 ds for lipase, and 58.32 ± 0.78 U g-1 ds for chitinase. These findings highlight the potential and versatility of mixed SSF using cost-effective agricultural waste for biopesticide and hydrolytic enzyme production, while promoting sustainable waste management and environmental pollution control, aligning with circular economy principles.

Culturomics- and metagenomics-based insights into the soil microbiome preservation and application for sustainable agriculture

Soil health is crucial for global food production in the context of an ever-growing global population. Microbiomes, a combination of microorganisms and their activities, play a pivotal role by biodegrading contaminants, maintaining soil structure, controlling nutrients' cycles, and regulating the plant responses to biotic and abiotic stresses. Microbiome-based solutions along the soil-plant continuum, and their scaling up from laboratory experiments to field applications, hold promise for enhancing agricultural sustainability by harnessing the power of microbial consortia. Synthetic microbial communities, i.e., selected microbial consortia, are designed to perform specific functions. In contrast, natural communities leverage indigenous microbial populations that are adapted to local soil conditions, promoting ecosystem resilience, and reducing reliance on external inputs. The identification of microbial indicators requires a holistic approach. It is fundamental for current understanding the soil health status and for providing a comprehensive assessment of sustainable land management practices and conservation efforts. Recent advancements in molecular technologies, such as high-throughput sequencing, revealed the incredible diversity of soil microbiomes. On one hand, metagenomic sequencing allows the characterization of the entire genetic composition of soil microbiomes, and the examination of their functional potential and ecological roles; on the other hand, culturomics-based approaches and metabolic fingerprinting offer complementary information by providing snapshots of microbial diversity and metabolic activities both in and ex-situ. Long-term storage and cryopreservation of mixed culture and whole microbiome are crucial to maintain the originality of the sample in microbiome biobanking and for the development and application of microbiome-based innovation. This review aims to elucidate the available approaches to characterize diversity, function, and resilience of soil microbial communities and to develop microbiome-based solutions that can pave the way for harnessing nature's untapped resources to cultivate crops in healthy soils, to enhance plant resilience to abiotic and biotic stresses, and to shape thriving ecosystems unlocking the potential of soil microbiomes is key to sustainable agriculture. Improving management practices by incorporating beneficial microbial consortia, and promoting resilience to climate change by facilitating adaptive strategies with respect to environmental conditions are the global challenges of the future to address the issues of climate change, land degradation and food security.

Agricultural Pest Management: The Role of Microorganisms in Biopesticides and Soil Bioremediation

Pesticide use in crops is a severe problem in some countries. Each country has its legislation for use, but they differ in the degree of tolerance for these broadly toxic products. Several synthetic pesticides can cause air, soil, and water pollution, contaminating the human food chain and other living beings. In addition, some of them can accumulate in the environment for an indeterminate amount of time. The agriculture sector must guarantee healthy food with sustainable production using environmentally friendly methods. In this context, biological biopesticides from microbes and plants are a growing green solution for this segment. Several pests attack crops worldwide, including weeds, insects, nematodes, and microorganisms such as fungi, bacteria, and viruses, causing diseases and economic losses. The use of bioproducts from microorganisms, such as microbial biopesticides (MBPs) or microorganisms alone, is a practice and is growing due to the intense research in the world. Mainly, bacteria, fungi, and baculoviruses have been used as sources of biomolecules and secondary metabolites for biopesticide use. Different methods, such as direct soil application, spraying techniques with microorganisms, endotherapy, and seed treatment, are used. Adjuvants like surfactants, protective agents, and carriers improve the system in different formulations. In addition, microorganisms are a tool for the bioremediation of pesticides in the environment. This review summarizes these topics, focusing on the biopesticides of microbial origin.

A review on fungal-based biopesticides and biofertilizers production

The escalating use of inorganic fertilizers and pesticides to boost crop production has led to the depletion of natural resources, contamination of water sources, and environmental crises. In response, the scientific community is exploring eco-friendly alternatives, such as fungal-based biofertilizers and biopesticides, which have proven effectiveness in enhancing plant health and growth while sustainably managing plant diseases and pests. This review article examines the production methodologies of these bioproducts, highlighting their role in sustainable agriculture and advancing our understanding of soil microorganisms. Despite their increasing demand, their global market presence remains limited compared to traditional chemical counterparts. The article addresses: 1) the production of biofertilizers and biopesticides, 2) their contribution to crop productivity, 3) their environmental impact and regulations, and 4) current production technologies. This comprehensive approach aims to promote the transition towards more sustainable agricultural practices.

Microbial Bioherbicides Based on Cell-Free Phytotoxic Metabolites: Analysis and Perspectives on Their Application in Weed Control as an Innovative Sustainable Solution

Weeds cause significant agricultural losses worldwide, and herbicides have traditionally been the main solution to this problem. However, the extensive use of herbicides has led to multiple cases of weed resistance, which could generate an increase in the application concentration and consequently a higher persistence in the environment, hindering natural degradation processes. Consequently, more environmentally friendly alternatives, such as microbial bioherbicides, have been sought. Although these bioherbicides are promising, their efficacy remains a challenge, as evidenced by their limited commercial and industrial production. This article reviews the current status of microbial-based bioherbicides and highlights the potential of cell-free metabolites to improve their efficacy and commercial attractiveness. Stirred tank bioreactors are identified as the most widely used for production-scale submerged fermentation. In addition, the use of alternative carbon and nitrogen sources, such as industrial waste, supports the circular economy. Furthermore, this article discusses the optimization of downstream processes using bioprospecting and in silico technologies to identify target metabolites, which leads to more precise and efficient production strategies. Bacterial bioherbicides, particularly those derived from Pseudomonas and Xanthomonas, and fungal bioherbicides from genera such as Alternaria, Colletotrichum, Trichoderma and Phoma, show significant potential. Nevertheless, limitations such as their restricted range of action, their persistence in the environment, and regulatory issues restrict their commercial availability. The utilization of cell-free microbial metabolites is proposed as a promising solution due to their simpler handling and application. In addition, modern technologies, including encapsulation and integrated management with chemical herbicides, are investigated to enhance the efficacy and sustainability of bioherbicides.

Bioprocess optimization for food-grade cellulolytic enzyme production from sorghum waste in a novel solid-state fermentation bioreactor for enhanced apple juice clarification

Transforming global agricultural waste into eco-friendly products like industrial enzymes through bioconversion can help address sustainability challenges aligning with the United Nations' Sustainable Development Goals. Present study explored the production of high-yield food-grade cellulolytic enzymes from Trichoderma reesei MTCC 4876, using a novel media formulation with a combination of waste sorghum grass and cottonseed oil cake (3:1). Optimization of physical and environmental parameters, along with the screening and optimization of media components, led to an upscaled process in a novel 6-L solid-state fermentation (SSF)-packed bed reactor (PBR) with a substrate loading of 200 g. Saturated forced aeration proved crucial, resulting in high fungal biomass (31.15 ± 0.63 mg glucosamine/gm dry fermented substrate) and high yield cellulase (20.64 ± 0.36 FPU/g-ds) and xylanase (16,186 ± 912 IU/g-ds) production at an optimal airflow rate of 0.75 LPM. The PBR exhibited higher productivity than shake flasks for all the enzyme systems. Microfiltration and ultrafiltration of the crude cellulolytic extract achieved 94% and 71% recovery, respectively, with 13.54 FPU/mL activity in the cellulolytic enzyme concentrate. The concentrate displayed stability across wide pH and temperature ranges, with a half-life of 24.5-h at 50 °C. The cellulase concentrate, validated for food-grade safety, complies with permissible limits for potential pathogens, heavy metals, mycotoxins, and pesticide residue. It significantly improved apple juice clarity (94.37 T%) by reducing turbidity (21%) and viscosity (99%) while increasing total reducing sugar release by 63% compared with untreated juice. The study also highlighted the potential use of lignin-rich fermented end residue for fuel pellets within permissible SOx emission limits, offering sustainable biorefinery prospects. Utilizing agro wastes in a controlled bioreactor environment underscores the potential for efficient large-scale cellulase production, enabling integration into food-grade applications and presenting economic benefits to fruit juice industries.

Fungus-based bioherbicides on circular economy

This review aimed to show that bioherbicides are possible in organic agriculture as natural compounds from fungi and metabolites produced by them. It is discussed that new formulations must be developed to improve field stability and enable the commercialization of microbial herbicides. Due to these bottlenecks, it is crucial to advance the bioprocesses behind the formulation and fermentation of bio-based herbicides, scaling up, strategies for field application, and the potential of bioherbicides in the global market. In this sense, it proposed insights for modern agriculture based on sustainable development and circular economy, precisely the formulation, scale-up, and field application of microbial bioherbicides.

Conidia production of the entomopathogenic fungus Beauveria bassiana using packed-bed bioreactor: Effect of substrate biodegradability on conidia virulence

This work presents the scale-up of the conidia production of the entomopathogenic fungus Beauveria bassiana using two different wastes, coupled with concentration and virulence tests of the produced conidia against the pest Tenebrio molitor. Beauveria bassiana CECT 20374 was used in solid state fermentation (SSF) operating under batch strategy. Two substrates with different biodegradability (rice husk and beer draff) were tested, successfully scaling from 1.5 L to 22 L bioreactors. Higher conidia production was reached using beer draff as substrate (2.5 × 10⁹ and 6.0 × 10⁸ conidia g^-1 dry matter in 1.5 and 22 L reactors respectively) highlighting air free porosity relevance as scale-up parameter. Concentration and dose-response tests against larvae and adult Tenebrio molitor were performed to compare strain CECT 20374 with control strain KVL 13-39 (a B. bassiana strain previously tested against T. molitor). Virulence effect of the 22 L fermentation product of strain CECT using rice husk or beer draff was tested against T. molitor adult stage. However, quality loses between conidia produced in agar plates and fermented products were observed (from 75 to 80% mortality in plates to 40% in rice husk and 50-60% in beer draff fermented products respectively). The differences between plate and fermented samples also indicated fermentation process, extraction and conservation steps as possible causes for quality losses, highlighting the need to optimize them to maximize virulence maintenance.

Trichoderma as a biological control agent: mechanisms of action, benefits for crops and development of formulations

Currently, the food and economic losses generated by the attack of phytopathogens on the agricultural sector constitute a severe problem. Conventional crop protection techniques based on the application of synthetic pesticides to combat these undesirable microorganisms have also begun to represent an inconvenience since the excessive use of these substances is associated with contamination problems and severe damage to the health of farmers, consumers, and communities surrounding the fields, as well as the generation of resistance by the phytopathogens to be combated. Using biocontrol agents such as Trichoderma to mitigate the attack of phytopathogens represents an alternative to synthetic pesticides, safe for health and the environment. This work explains the mechanisms of action through which Trichoderma exerts biological control, some of the beneficial aspects that it confers to the development of crops through its symbiotic interaction with plants, and the bioremedial effects that it presents in fields contaminated by synthetic pesticides. Also, detail the production of spore-based biopesticides through fermentation processes and formulation development.

Spent Grain: A Functional Ingredient for Food Applications

Spent grain is the solid fraction remaining after wort removal. It is nutritionally rich, composed of fibers—mainly hemicellulose, cellulose, and lignin—proteins, lipids, vitamins, and minerals, and must be managed properly. Spent grain is a by-product with high moisture, high protein and high fiber content and is susceptible to microbial contamination; thus, a suitable, cost-effective, and environmentally friendly valorization method of processing it is required. This by-product is used as a raw material in the production of many other food products—bakery products, pasta, cookies, muffins, wafers, snacks, yogurt or plant-based yogurt alternatives, Frankfurter sausages or fruit beverages—due to its nutritional values. The circular economy is built on waste reduction and the reuse of by-products, which find opportunities in the regeneration and recycling of waste materials and energy that become inputs in other processes and food products. Waste disposal in the food industry has become a major issue in recent years when attempting to maintain hygiene standards and avoid soil, air and water contamination. Fortifying food products with spent grain follows the precepts of the circular bio-economy and industrial symbiosis of strengthening sustainable development. The purpose of this review is to update information on the addition of spent grain to various foods and the influence of spent grain on these foods.

Valorization of agro-industrial wastes for biorefinery process and circular bioeconomy: A critical review

Energy recovery from waste resources is a promising approach towards environmental consequences. In the prospect of environmental sustainability, utilization of agro-industrial waste residues as feedstock for biorefinery processes have gained widespread attention. In the agro-industry, various biomasses are exposed to different unit processes for offering value to various agro-industrial waste materials. Agro-industrial wastes can generate a substantial amount of valuable products such as fuels, chemicals, energy, electricity, and by-products. This paper reviews the methodologies for valorization of agro-industrial wastes and their exploitation for generation of renewable energy products. In addition, management of agro-industrial wastes and products from agro-industrial wastes have been elaborated. The waste biorefinery process using agro-industrial wastes does not only offer energy, it also offers environmentally sustainable modes, which address effective management of waste streams. This review aims to highlight the cascading use of biomass from agro-industrial wastes into the systemic approach for economic development.