Microbial itaconic acid production from starchy food waste by newly isolated thermotolerant Aspergillus terreus strain

Valorization of sugarcane bagasse for high-yield production of laccase through Aspergillus terreus for effective azo dye decolourization

Synthetic dyes such as azo dyes are significant pollutants in the wastewater released from various textile industries. The low biodegradability and production from synthetic sources with high shelf life make azo dyes a challenging material for degradation. This study used chemically mutated Aspergillus terrus in the laccase production under solid-state fermentation using sugarcane bagasse. Initially, the wild-type strain produced a laccase activity of 4.12 U/mL. Later, the alkaline pretreatment of sugarcane bagasse showed a significant increase in laccase activity by 38.9%. Further, random mutagenesis treatment with 100 mM EMS generated a hyper laccase-producing strain with a 2.3-fold increment in laccase activity compared to the wild-type strain. The enzyme displayed optimal activity at pH 6.5 and 35 °C. The metal ions such as Fe3+ (29.4 U/mL), Fe2+ (20.8 U/mL) and Cu2+ (18.05 U/mL) showed positive effects on laccase activity. The crude laccase was used to bioremediate Congo red, a prominent azo dye used in textile and pharmaceutical industries. The preliminary studies with a crude enzyme displayed 68.86% dye decolourization after 24 h of incubation. Additionally, with Taguchi orthogonal array optimization experiments, the maximal dye decolorization of 78.24% was achieved by maintaining crude enzyme concentration (20 U), dye concentration (25 mg/L) and pH 4.5.

Mixed food waste valorization using a thermostable glucoamylase enzyme produced by a newly isolated filamentous fungus: A sustainable biorefinery approach

Food waste is a lucrative source of complex nutrients, which can be transformed into a multitude of bioproducts by the aid of microbial cell factories. The current study emphasizes isolating Glucoamylase enzyme (GA) producing strains that can effectively break down mixed food waste (MW), which serves as a substrate for biomanufacturing. The screening procedure relied heavily on the growth of isolated fungi on starch agar media, to specifically identify the microbes with the highest starch hydrolysis potential. A strain displayed the highest GA activity of 2.9 ± 0.14 U/ml which was selected and identified as Aspergillus fumigatus via molecular methods of identification. Exposure of the A. fumigatus with 200 mM Ethyl methanesulphonate (EMS) led to a 23.79% increase compared to the wild-type GA. The growth conditions like cultivation temperature or the number of spores in the inoculum were investigated. Further, maximum GA activity was exhibited at pH 5, 55 °C, and at 5 mM Ca2+ concentration. The GA showed thermostability, retaining activity even after long periods of exposure to temperatures as high as 95 °C. The improvement of hydrolysis of MW was achieved by Taguchi design where a maximum yield of 0.57 g g-1 glucose was obtained in the hydrolysate. This study puts forth the possibility that mixed food waste, despite containing spices and other microbial growth-inhibitory substances, can be efficiently hydrolyzed to release glucose units, by robust fungal cell factories. The glucose released can then be utilized as a carbon source for the production of value-added products.

Establishing an itaconic acid production process with Ustilago species on the low-cost substrate starch

Ustilago maydis and Ustilago cynodontis are natural producers of a broad range of valuable molecules including itaconate, malate, glycolipids, and triacylglycerols. Both Ustilago species are insensitive toward medium impurities, and have previously been engineered for efficient itaconate production and stabilized yeast-like growth. Due to these features, these strains were already successfully used for the production of itaconate from different alternative feedstocks such as molasses, thick juice, and crude glycerol. Here, we analyzed the amylolytic capabilities of Ustilago species for metabolization of starch, a highly abundant and low-cost polymeric carbohydrate widely utilized as a substrate in several biotechnological processes. Ustilago cynodontis was found to utilize gelatinized potato starch for both growth and itaconate production, confirming the presence of extracellular amylolytic enzymes in Ustilago species. Starch was rapidly degraded by U. cynodontis, even though no α-amylase was detected. Further experiments indicate that starch hydrolysis is caused by the synergistic action of glucoamylase and α-glucosidase enzymes. The enzymes showed a maximum activity of around 0.5 U ml-1 at the fifth day after inoculation, and also released glucose from additional substrates, highlighting potential broader applications. In contrast to U. cynodontis, U. maydis showed no growth on starch accompanied with no detectable amylolytic activity.

Recent Progress in Metabolic Engineering of Escherichia coli for the Production of Various C4 and C5-Dicarboxylic Acids

As an alternative to petrochemical synthesis, well-established industrial microbes, such as Escherichia coli, are employed to produce a wide range of chemicals, including dicarboxylic acids (DCAs), which have significant potential in diverse areas including biodegradable polymers. The demand for biodegradable polymers has been steadily rising, prompting the development of efficient production pathways on four- (C4) and five-carbon (C5) DCAs derived from central carbon metabolism to meet the increased demand via the biosynthesis. In this context, E. coli is utilized to produce these DCAs through various metabolic engineering strategies, including the design or selection of metabolic pathways, pathway optimization, and enhancement of catalytic activity. This review aims to highlight the recent advancements in metabolic engineering techniques for the production of C4 and C5 DCAs in E. coli.

Microbial itaconic acid bioproduction towards sustainable development: Insights, challenges, and prospects

Microbial biomanufacturing is a promising approach to produce high-value compounds with low-carbon footprint and significant economic benefits. Among twelve "Top Value-Added Chemicals from Biomass", itaconic acid (IA) stands out as a versatile platform chemical with numerous applications. IA is naturally produced by Aspergillus and Ustilago species through a cascade enzymatic reaction between aconitase (EC 4.2.1.3) and cis-aconitic acid decarboxylase (EC 4.1.1.6). Recently, non-native hosts such as Escherichia coli, Corynebacterium glutamicum, Saccharomyces cerevisiae, and Yarrowia lipolytica have been genetically engineered to produce IA through the introduction of key enzymes. This review provides an up-to-date summary of the progress made in IA bioproduction, from native to engineered hosts, covers in vivo and in vitro approaches, and highlights the prospects of combination tactics. Current challenges and recent endeavors are also addressed to envision comprehensive strategies for renewable IA production in the future towards sustainable development goals (SDGs).

Integrated fermentative production and downstream processing of L-malic acid by Aspergillus wentii using cassava peel waste

L-malic acid (L-MA) is an industrially significant chemical with enormous potential. The fungal cell factories could be exploited to harvest it on large scales. In our study, Aspergillus wentii strain (MTCC 1901 ^T) was explored for L-MA production. Initially, the L-MA production was carried out using glucose with optimization of parameters influencing product accumulation (pH and CaCO₃). The fermentation resulted in L-MA titer of 37.9 g/L with 0.39 g/g yield. Then, cassava peel waste (CPW) was used for L-MA production by separate hydrolysis and fermentation. Optimized acidic and enzymatic hydrolysis resulted in glucose release of 0.53 and 0.66 g/g CPW, respectively. The strain accumulated 20.9 g/L and 33.1 g/L L-MA with corresponding yields of 0.25 g/g and 0.34 g/g during batch cultivation using acid and enzyme hydrolysate, respectively. Finally, the produced L-MA was separated using an inexpensive solvent extraction method. Among various solvents used, n-butanol exhibited maximum L-MA extraction efficiency (31%).

Recent Advances on the Production of Itaconic Acid via the Fermentation and Metabolic Engineering

Itaconic acid (ITA) is one of the top 12 platform chemicals. The global ITA market is expanding due to the rising demand for bio-based unsaturated polyester resin and its non-toxic qualities. Although bioconversion using microbes is the main approach in the current industrial production of ITA, ecological production of bio-based ITA faces several issues due to: low production efficiency, the difficulty to employ inexpensive raw materials, and high manufacturing costs. As metabolic engineering advances, the engineering of microorganisms offers a novel strategy for the promotion of ITA bio-production. In this review, the most recent developments in the production of ITA through fermentation and metabolic engineering are compiled from a variety of perspectives, including the identification of the ITA synthesis pathway, the metabolic engineering of natural ITA producers, the design and construction of the ITA synthesis pathway in model chassis, and the creation, as well as application, of new metabolic engineering strategies in ITA production. The challenges encountered in the bio-production of ITA in microbial cell factories are discussed, and some suggestions for future study are also proposed, which it is hoped offers insightful views to promote the cost-efficient and sustainable industrial production of ITA.

Integrated biorefineries for repurposing of food wastes into value-added products

Food waste (FW) generated through various scenarios from farm to fork causes serious environmental problems when either incinerated or disposed inappropriately. The presence of significant amounts of carbohydrates, proteins, and lipids enable FW to serve as sustainable and renewable feedstock for the biorefineries. Implementation of multiple substrates and product biorefinery as a platform could pursue an immense potential of reducing costs for bio-based process and improving its commercial viability. The review focuses on conversion of surplus FW into range of value-added products including biosurfactants, biopolymers, diols, and bioenergy. The review includes in-depth description of various types of FW, their chemical and nutrient compositions, current valorization techniques and regulations. Further, it describes limitations of FW as feedstock for biorefineries. In the end, review discuss future scope to provide a clear path for sustainable and net-zero carbon biorefineries.

Biotechnological interventions in food waste treatment for obtaining value-added compounds to combat pollution

Over the last few decades, the globe is facing tremendous effects due to the unnecessary piling of municipal solid waste among which food waste holds a greater portion. This practice not only affects the environment in terms of generating greenhouse gas emissions but when left dumped in landfills will also trigger poverty and malnutrition. This review focuses on the global trend in food waste management strategies involved in the effective utilization of food waste to produce various value-added products in a microbiology aspect, thereby diminishing the negative impacts caused by the unnecessary side effects of non-renewable energy sources. The review also detailed the efficiency of microorganisms in the production of various bio-energies as well. Further, recent attempts to the exploitation of genetically modified microorganisms in producing value-added products were enlisted. This also attempted to address food waste valorization techniques, the combined applications of various processes for an enhanced yield of different compounds, and addressed various challenges. Further, the current challenges involved in various processes and the effective measures to tackle them in the future have been addressed. Thus, the present review has successfully addressed the circular bio-economy in food waste valorization.

Myco-biorefinery approaches for food waste valorization: Present status and future prospects

Increases in population and urbanization leads to generation of a large amount of food waste (FW) and its effective waste management is a major concern. But putrescible nature and high moisture content is a major limiting factor for cost effective FW valorization. Bioconversion of FW for the production of value added products is an eco-friendly and economically viable strategy for addressing these issues. Targeting on production of multiple products will solve these issues to greater extent. This article provides an overview of bioconversion of FW to different value added products.

Rapid and mass production of biopesticide Trichoderma Brev T069 from cassava peels using newly established solid-state fermentation bioreactor system

Converting agricultural waste into value-added biopesticides to replace chemical pesticides for plant protection is a good alternative for environmental sustainability and resource recycling. In this study, five tropical wastes (cassava peels, banana pseudostem, coconut shell, sugarcane bagasse, and pineapple peels) were screened as substrates for the rapid production of biopesticide Trichoderma Brev T069. Five single tests and a Box-Behnken design (BBD) with response surface methodology were used to optimize the culture conditions to improve the spore yield. The results showed that cassava peel was the optimal solid fermentation substrate, and the optimization enabled a spore yield of 9.31 × 10⁹ spores/g at 3rd day, which was equal to 93.19% of spore yield obtained at 5th day (9.99 × 10⁹ spores/g). A newly packed-bed bioreactor with agitation and ventilation system was developed and used to expand the production that 250 kg of biopesticide (2.89 × 10⁹ spores/g) could be available on the 3rd day. A pot experiment indicated that the biopesticide T. Brev T069 obtained under this production system, when applied at 1 × 10⁷ spores/g of soil had a 64.65% biocontrol efficiency on banana fusarium wilt. This study provides a practical solution for turning a tropical waste into an effective biopesticide which can prevent banana wilt disease, thereby helping to reduce disease management cost and overcome environmental hazards caused by synthetic pesticides.

Recent Advances in Biotechnological Itaconic Acid Production, and Application for a Sustainable Approach

Intense research has been conducted to produce environmentally friendly biopolymers obtained from renewable feedstock to substitute fossil-based materials. This is an essential aspect for implementing the circular bioeconomy strategy, expressly declared by the European Commission in 2018 in terms of "repair, reuse, and recycling". Competent carbon-neutral alternatives are renewable biomass waste for chemical element production, with proficient recyclability properties. Itaconic acid (IA) is a valuable platform chemical integrated into the first 12 building block compounds the achievement of which is feasible from renewable biomass or bio-wastes (agricultural, food by-products, or municipal organic waste) in conformity with the US Department of Energy. IA is primarily obtained through fermentation with Aspergillus terreus, but nowadays several microorganisms are genetically engineered to produce this organic acid in high quantities and on different substrates. Given its trifunctional structure, IA allows the synthesis of various novel biopolymers, such as drug carriers, intelligent food packaging, antimicrobial biopolymers, hydrogels in water treatment and analysis, and superabsorbent polymers binding agents. In addition, IA shows antimicrobial, anti-inflammatory, and antitumor activity. Moreover, this biopolymer retains qualities like environmental effectiveness, biocompatibility, and sustainability. This manuscript aims to address the production of IA from renewable sources to create a sustainable circular economy in the future. Moreover, being an essential monomer in polymer synthesis it possesses a continuous provocation in the biopolymer chemistry domain and technologies, as defined in the present review.

Recycling bread waste into chemical building blocks using a circular biorefining approach

Food waste is a global problem, causing significant environmental harm and resulting in substantial economic losses globally. Bread is the commonly wasted food item in the developed world and presents a severe problem for the majority of European nations. It is the second most wasted food item in the UK after potatoes, with an equivalent of 20 million slices of bread thrown away daily. Bread is a starchy material and a rich and clean source of easily extractable fermentable sugars - this is in direct contrast to lignocellulosic feedstocks where harsh physical, chemical and/or enzymatic pretreatment processes are required for release of fermentable sugars. Furthermore, these necessary lignocellulosic pretreatment methods often produce sugars contaminated with fermentation inhibitors. Therefore, bread waste presents a clear opportunity as a potential carbon source for novel commercial processes and, to this end, several alternative routes have been developed to utilize bread waste. Possibilities for direct recycling of bread waste within the food industry are limited due to the relatively short material lifetime, stringent process and hygiene requirements. Anaerobic digestion (AD) and incineration are commonly employed methods for the valorisation of bread waste, generating limited amounts of green energy but with little other environmental or economic benefits. Most food wastes and by-products in the UK including bakery waste are treated through AD processes that fail to harness the full potential of the these wastes. This short communication reviews the challenges of handling bread waste, with a focus on a specific UK scenario. The review will consider how bread waste is generated across the supply chain, current practices to deal with the waste and logistics challenges in waste collection. The presence of clean and high-quality fermentable sugars, proteins and other nutrients in bread make it an ideal substrate for generating chemicals, fuels, bioplastics, pharmaceuticals and other renewable products through microbial fermentations. We suggest potential applications for recycling bread waste into its chemical building blocks through a fermentative route where a circular biorefining approach could maximize resource recovery and environmental savings and eliminate waste to as close to zero as possible.

Engineered production of pyridoxal 5'-phosphate in Escherichia coli BL21

Pyridoxal 5'-phosphate (PLP) is the coenzyme of more than 140 enzymes and is widely used in various fields. In this study, to enhance the production of PLP in Escherichia coli BL21, the recombinant strain E. coli BL21/pETDuet-1-pdxj-zwf-dxs was constructed. The concentration of PLP in this strain was 82.69 mg/L, which was increased by 1.38-fold as compared to that in E. coli BL21. Glucose, yeast extract, and pH had an obvious impact on the concentration of PLP, and their optimal levels were 34.89 g/L, 31.17 g/L, and 10.07, respectively. The concentration of PLP under the optimal condition reached 2.23 g/L. The time-course analysis showed that the highest concentration of PLP was 2.32 g/L in recombinant strain after the induction for 12 h by 0.1 mM IPTG in a 1 L shake flask, which was increased by 38.76-fold as compared to that in E. coli BL21. This study provides a good basis for the efficient production of PLP in E. coli BL21.