Abstract: Lipases are versatile biocatalysts and are used in different bioconversion reactions. Microbial lipases are currently attracting a great amount of attention due to the rapid advancement of enzyme technology and its practical application in a variety of industrial processes. The current review provides updated information on the different sources of microbial lipases, such as fungi, bacteria, and yeast, their classical and modern purification techniques, including precipitation and chromatographic separation, the immunopurification technique, the reversed micellar system, aqueous two-phase system (ATPS), aqueous two-phase flotation (ATPF), and the use of microbial lipases in different industries, e.g., the food, textile, leather, cosmetics, paper, and detergent industries. Furthermore, the article provides a critical analysis of lipase-producing microbes, distinguished from the previously published reviews, and illustrates the use of lipases in biosensors, biodiesel production, and tea processing, and their role in bioremediation and racemization.

Abstract: Meeting the demands of the growing population requires increased food and feed production, leading to higher levels of agri-food waste. As this type of waste seriously threatens public health and the environment, novel approaches to waste management should be developed. Insects have been proposed as efficient agents for biorefining waste, producing biomass that can be used for commercial products. However, challenges in achieving optimal outcomes and maximizing beneficial results remain. Microbial symbionts associated with insects are known to have a critical role in the development, fitness, and versatility of insects, and as such, they can be utilized as targets for the optimization of agri-food waste insect-based biorefinery systems. This review discusses insect-based biorefineries, focusing on the agricultural applications of edible insects, mainly as animal feed and organic fertilizers. We also describe the interplay between agri-food waste-utilizing insects and associated microbiota and the microbial contribution in enhancing insect growth, development, and involvement in organic waste bioconversion processes. The potential contribution of insect gut microbiota in eliminating pathogens, toxins, and pollutants and microbe-mediated approaches for enhancing insect growth and the bioconversion of organic waste are also discussed. The present review outlines the benefits of using insects in agri-food and organic waste biorefinery systems, describes the roles of insect-associated microbial symbionts in waste bioconversion processes, and highlights the potential of such biorefinery systems in addressing the current agri-food waste-related challenges.

Abstract: The isomerization of xylose to xylulose is considered the most promising approach to initiate xylose bioconversion. Here, phylogeny-guided big data mining, rational modification, and ancestral sequence reconstruction strategies were implemented to explore new active xylose isomerases (XIs) for Saccharomyces cerevisiae. Significantly, 13 new active XIs for S. cerevisiae were mined or artificially created. Moreover, the importance of the amino-terminal fragment for maintaining basic XI activity was demonstrated. With the mined XIs, four efficient xylose-utilizing S. cerevisiae were constructed and evolved, among which the strain S. cerevisiae CRD5HS contributed to ethanol titers as high as 85.95 and 94.76 g/liter from pretreated corn stover and corn cob, respectively, without detoxifying or washing pretreated biomass. Potential genetic targets obtained from adaptive laboratory evolution were further analyzed by sequencing the high-performance strains. The combined XI mining methods described here provide practical references for mining other scarce and valuable enzymes.

Abstract: Lignocellulosic biomasses (LCB) are sustainable and abundantly available feedstocks for the production of biofuel and biochemicals via suitable bioconversion processing. The main aim of this review is to focus on strategies needed for the progression of viable lignocellulosic biomass-based biorefineries (integrated approaches) to generate biofuels and biochemicals. Processing biomass in a sustainable manner is a major challenge that demands the accomplishment of basic requirements relating to cost effectiveness and environmental sustainability. The challenges associated with biomass availability and the bioconversion process have been explained in detail in this review. Limitations associated with biomass structural composition can obstruct the feasibility of biofuel production, especially in mono-process approaches. In such cases, biorefinery approaches and integrated systems certainly lead to improved biofuel conversion. This review paper provides a summary of mono and integrated approaches, their limitations and advantages in LCB bioconversion to biofuel and biochemicals.

Abstract: Human population growth, industrialization, and globalization have caused several pressures on the planet’s natural resources, culminating in the severe climate and environmental crisis which we are facing. Aiming to remedy and mitigate the impact of human activities on the environment, the use of lignocellulolytic enzymes for biofuel production, food, bioremediation, and other various industries, is presented as a more sustainable alternative. These enzymes are characterized as a group of enzymes capable of breaking down lignocellulosic biomass into its different monomer units, making it accessible for bioconversion into various products and applications in the most diverse industries. Among all the organisms that produce lignocellulolytic enzymes, microorganisms are seen as the primary sources for obtaining them. Therefore, this review proposes to discuss the fundamental aspects of the enzymes forming lignocellulolytic systems and the main microorganisms used to obtain them. In addition, different possible industrial applications for these enzymes will be discussed, as well as information about their production modes and considerations about recent advances and future perspectives in research in pursuit of expanding lignocellulolytic enzyme uses at an industrial scale.

Abstract: Worldwide, a huge production of agro-industrial wastes is observed every year in the milling, brewing, agricultural, and food industries. Biochemical and bioactive substances can be produced from these agricultural wastes. Pineapple by-products, which consist of the peeled skin, core, crown end, etc., account for 60% of the weight of pineapple fruit and are disposed of as waste, causing disposal and pollution problems. The bioconversion process can utilize these wastes, which are rich in cellulose and hemicellulose, the main components, to produce value-added biochemicals/bioactive compounds such as pectin, citric acid, bromelain, ferulic acid, vanillin, and so on. Therefore, the sustainable solution for food and nutrition security can be supported by the utilization of pineapple waste. The proposed review article addresses approaches that do not generate waste while adding value. This can be achieved by using innovative biorefinery techniques such as green extraction and the use of green solvents. Microbial fermentation with an effective pretreatment (such as hydrothermal treatment and enzymatic treatment) to convert complex waste (pineapple fruit) into simple sugars and later fuel production are also discussed. The proposed review also provides a concise overview of the most recent research and developments in the field of advanced pineapple waste processing technologies.

Abstract: Black soldier fly (BSF) (Hermetia illucens) larvae are currently being developed as bioconversion agents for organic waste treatment. The resulting larvae or prepupae have a high protein and lipid content, primarily used as feed for fish, poultry, and other animals. The lipid content of BSF larvae/prepupae is influenced by the feed for growth and can reach up to 57.8%. BSF lipids mainly consist of medium-chain saturated fatty acids, with lauric acid (LA) being the dominant component. The LA content in BSF larvae/prepupae can be enhanced by incorporating or utilizing substrates containing highly digestible carbohydrates for larval growth. The LA content can reach 76.13% in larvae reared on fruit waste. LA has been reported to exhibit antibacterial, antifungal, antiviral, and anticancer properties. Moreover, it has applications in various fields such as pharmaceuticals, food and beverages, cosmetics, body care, soaps and detergents, plastics, and textiles. This review aims to investigate the LA content in BSF larvae and explore its potential applications, thereby establishing BSF larvae/prepupae as a novel source of LA for diverse fields.

Abstract: In recent years, microbial conversion of inorganic selenium into an efficient and low-toxic form of selenium has attracted much attention. With the improvement of scientific awareness and the continuous progress of nanotechnology, selenium nanoparticles can not only play the unique functions of organic selenium and inorganic selenium but also have higher safety, absorption and biological activity than other selenium forms. Therefore, the focus of attention has gradually shifted beyond the level of selenium enrichment in yeast to the combination of biosynthetic selenium nanoparticles (BioSeNPs). This paper primarily reviews inorganic selenium and its conversion to less toxic organic selenium and BioSeNPs by microbes. The synthesis method and potential mechanism of organic selenium and BioSeNPs are also introduced, which provide a basis for the production of specific forms of selenium. The methods to characterize selenium in different forms are discussed to understand the morphology, size and other characteristics of selenium. In general, to obtain safer and higher selenium content products, it is necessary to develop yeast resources with higher selenium conversion and accumulation.

Abstract: Succinic acid (SA) is an intermediate product of the tricarboxylic acid cycle (TCA) and is one of the most significant platform chemicals for the production of various derivatives with high added value. Due to the depletion of fossil raw materials and the demand for eco-friendly energy sources, SA biosynthesis from renewable energy sources is gaining attention for its environmental friendliness. This review comprehensively analyzes strategies for the bioconversion of lignocellulose to SA based on the lignocellulose pretreatment processes and cellulose hydrolysis and fermentation principles and highlights the research progress on acid production and SA utilization under different microbial culture conditions. In addition, the fermentation efficiency of different microbial strains for the production of SA and the main challenges were analyzed. The future application directions of SA derivatives were pointed out. It is expected that this research will provide a reference for the optimization of SA production from lignocellulose.

Abstract: Lignocellulosic biorefinery has long been recognized as a potential strategy for sustainable production of biofuels, materials and chemicals. These productions in many cases rely on pretreatment and enzymatic hydrolysis of lignocellulosic carbohydrates, whereas the low degradation efficiency and high enzyme dosage are challenging bottlenecks of economically industrial production. The complex recalcitrant nature of lignocellulose requires a well-matched enzyme cocktail to achieve complete and efficient degradation. Numerous studies have investigated the relationship between biomass components, structural properties and enzymes synergistic action in the past decades. This article aims to present a comprehensive review on this subject by introducing recent advances in substrate modification techniques, underlying mechanisms of enzyme synergism and governing factors in structure-activity interaction. In addition, newly developed modellings and multi-omic analysis techniques for preparing commercial enzyme preparations are introduced, revealing possible avenues for achieving economic viability of lignocellulose bioconversion.

Abstract: Combustion and depletion of fossil fuels, open burning of agricultural wastes, and use of hazardous chemicals in biofuels production route are some major challenges among scientific community. In the present study these obstacles were mitigated simultaneously. Initially, rice straw biomass was delignified using a combined eco-friendly laccase-assisted sodium chlorite (LASC) pretreatment. The combined pretreatment strategy of rice straw biomass reduced 55.6% lignin and increased the total available carbohydrate by 1.43 fold. Further, enzymatic digestion of LASC pretreated rice straw using a formulated cellulase cocktail from Aspergillus flavus MDU-5 and Trichoderma citrinoviride MDU-1 liberated 526.68 mg/g sugars with high saccharification yield (84.0%). The enzymatic hydrolysates thus obtained were found to contain 7.43–16.78 g/L sugars. The cellulolytic hydrolysates when fermented with Saccharomyces cerevisiae NCIM-3640 produced 3.02–7.28 g/L bioethanol, with high yield (72.96–85.31% of the theoretical value). Parallelly, lignin extracted from waste pretreatment stream showed biopesticidal activity against the larvae of H. armigera; whereas, the evaluation of residual material (after hydrolysis and fermentation) exhibited biofertilizer properties. These findings suggests that the environmentally benign LASC pretreatment, cellulase cocktail, and utilization of waste stream for the production of biopesticide and biofertilizer may provide a promising strategy in the development of holistic lignocellulosic biorefinery process.

Abstract: Landfill leachate (LFL) treatment is a severe challenge due to its highly viscous nature and various complex pollutants. Leachate comprises various toxic pollutants, including inorganic macro/nano components, xenobiotics, dissolved organic matter, heavy metals, and microorganisms responsible for severe environmental pollution. Various treatment procedures are available to achieve better effluent quality levels; however, most of these treatments are nondestructive, so pollutants are merely transported from one phase to another, resulting in secondary contamination. Anaerobic digestion is a promising bioconversion technology for treating leachate while producing renewable, cleaner energy. Because of its high toxicity and low biodegradability, biological approaches necessitate employing other techniques to complement and support the primary process. In this regard, pretreatment technologies have recently attracted researchers’ interest in addressing leachate treatment concerns through anaerobic digestion. This review summarizes various LFL pretreatment methods, such as electrochemical, ultrasonic, alkaline, coagulation, nanofiltration, air stripping, adsorption, and photocatalysis, before the anaerobic digestion of leachate. The pretreatment could assist in converting biogas (carbon dioxide to methane) and residual volatile fatty acids to valuable chemicals and fuels and even straight to power generation. However, the selection of pretreatment is a vital step. The techno-economic analysis also suggested the high economic feasibility of integrated-anaerobic digestion. Therefore, with the incorporation of pretreatment and anaerobic digestion, the process could have high economic viability attributed to bioenergy production and cost savings through sustainable leachate management options.

Abstract: The seafood industry generates waste, including shells, bones, intestines, and wastewater. The discards are nutrient-rich, containing varying concentrations of carotenoids, proteins, chitin, and other minerals. Thus, it is imperative to subject seafood waste, including shrimp waste (SW), to secondary processing and valorization for demineralization and deproteination to retrieve industrially essential compounds. Although several chemical processes are available for SW processing, most of them are inherently ecotoxic. Bioconversion of SW is cost-effective, ecofriendly, and safe. Microbial fermentation and the action of exogenous enzymes are among the significant SW bioconversion processes that transform seafood waste into valuable products. SW is a potential raw material for agrochemicals, microbial culture media, adsorbents, therapeutics, nutraceuticals, and bio-nanomaterials. This review comprehensively elucidates the valorization approaches of SW, addressing the drawbacks of chemically mediated methods for SW treatments. It is a broad overview of the applications associated with nutrient-rich SW, besides highlighting the role of major shrimp-producing countries in exploring SW to achieve safe, ecofriendly, and efficient bio-products.

Abstract: Simple Summary Bioconversion of chitinous waste to chito-oligosaccharides using chitinase is an attractive strategy for traditional waste management. Chito-oligosaccharides have a broad range of applications due to their water solubility and possess various biological properties. The different sources of chitinase provide different yields and physicochemical properties, e.g., the degree of polymerization of chito-oligosaccharides. This review discusses the potential of chitinase in chito-oligosaccharide production with a focus on the chitinase sources, chemo-enzymatic production of chito-oligosaccharides and their derivatives, applications of chito-oligosaccharides, and the route to industrialization, based on the academic studies published within the most recent decade. Abstract Chito-oligosaccharides (COSs) are the partially hydrolyzed products of chitin, which is abundant in the shells of crustaceans, the cuticles of insects, and the cell walls of fungi. These oligosaccharides have received immense interest in the last few decades due to their highly promising bioactivities, such as their anti-microbial, anti-tumor, and anti-inflammatory properties. Regarding environmental concerns, COSs are obtained by enzymatic hydrolysis by chitinase under milder conditions compared to the typical chemical degradation. This review provides updated information about research on new chitinase derived from various sources, including bacteria, fungi, plants, and animals, employed for the efficient production of COSs. The route to industrialization of these chitinases and COS products is also described.