Insights into using green and unconventional technologies to recover natural astaxanthin from microbial biomass

Advancements of astaxanthin production in Haematococcus pluvialis: Update insight and way forward

The global market demand for natural astaxanthin (AXT) is growing rapidly owing to its potential human health benefits and diverse industry applications, driven by its safety, unique structure, and special function. Currently, the alga Haematococcus pluvialis (alternative name H. lacustris) has been considered as one of the best large-scale producers of natural AXT. However, the industry's further development faces two main challenges: the limited cultivation areas due to light-dependent AXT accumulation and the low AXT yield coupled with high production costs resulting from complex, time-consuming upstream biomass culture and downstream AXT extraction processes. Therefore, it is urgently to develop novel strategies to improve the AXT production in H. pluvialis to meet industrial demands, which makes its commercialization cost-effective. Although several strategies related to screening excellent target strains, optimizing culture condition for high biomass yield, elucidating the AXT biosynthetic pathway, and exploiting effective inducers for high AXT content have been applied to enhance the AXT production in H. pluvialis, there are still some unsolved and easily ignored perspectives. In this review, firstly, we summarize the structure and function of natural AXT focus on those from the algal H. pluvialis. Secondly, the latest findings regarding the AXT biosynthetic pathway including spatiotemporal specificity, transport, esterification, and storage are updated. Thirdly, we systematically assess enhancement strategies on AXT yield. Fourthly, the regulation mechanisms of AXT accumulation under various stresses are discussed. Finally, the integrated and systematic solutions for improving AXT production are proposed. This review not only fills the existing gap about the AXT accumulation, but also points the way forward for AXT production in H. pluvialis.

Microalgae-derived astaxanthin: bioactivities, biotechnological approaches and industrial technologies for its production

Microalgae are rich sources of astaxanthin well recognized for their potent bioactivities such as antioxidant, anti-cancer, and anti-inflammatory activities. Recent interests focused on the bioactivities of microalgae-derived astaxanthin on treating or preventing cancers mediated by their antioxidant and anti-inflammatory properties. This is due to the special structural configuration of microalgae-derived astaxanthin in terms of unsaturation (conjugated double bonds), stereochemical isomerism (3S,3'S optical isomer) and esterification (monoester), which display more potent bioactivities, compared with those from the other natural sources such as yeasts and higher plants, as well as synthetic astaxanthin. This review focuses on the recent advances on the bioactivities of microalgae-derived astaxanthin in association with cancers and immune diseases, with emphasis on their potential applications as natural antioxidants. Various well-developed biotechnological approaches for inducing astaxanthin production from microalgal culture, along with the proven and emerging industrial technologies to commercialize astaxanthin products in a large-scale manner, are also critically reviewed. These would facilitate the manufacture of bioactive microalgae-derived astaxanthin products to be applied in the food and pharmaceutical industries as salutary nutraceuticals.

Ultra-high-pressure homogenization combined with ionic liquid-organic acid solvent for effective pretreatment of lignocellulose biomass

The complex structure of lignocellulose necessitates advanced pretreatment techniques to effectively separate its three primary components for further conversion into valuable products. This study introduced an innovative approach to pretreating bagasse by commencing with ultra-high-pressure homogenization (UHPH) applied to raw bagasse, which maintained chemical integrity while reducing intermolecular bonds, crystallinity, and particle size. Subsequently, UHPH-bagasse underwent pretreatment using a synergistic solution of ionic liquid ([Bmim]Cl) and organic acid (oxalic acid: OA). This combination achieved a remarkable 90.26 % lignin removal rate, surpassing many conventional methods. The influence of temperature on pretreatment efficiency was also explored, demonstrating effective lignin removal at temperatures below 130 °C without compromising cellulose integrity. This performance greatly enhanced cellulose conversion into levulinic acid (from 38.8 % to 57.5). However, temperatures exceeding 140 °C led to lignin depolymerization and subsequent re-aggregation on the residue's surface, hindering cellulose conversion. The [Bmim]Cl-OA system not only aided bagasse delignification but also promoted cleavage of β-O-4' linkages, especially at higher temperatures. The resulting lignin exhibited reduced molecular weight and nanoscale particle size, enhancing its antioxidant properties and suggesting potential applications in lignin-based chemicals and materials.

Astaxanthin biosynthesis for functional food development and space missions

Astaxanthin (AXT), a natural carotenoid, has strong antioxidant and anti-ageing effects and can reduce ultraviolet light-induced damage to cells and DNA, stimulate the immune system, and improve cardiovascular disease prognosis. Despite its wide applications in the: nutraceutical, cosmetic, aquaculture, and pharmaceutical industries, AXT industrial production and application are hindered by natural source scarcity, low production efficiency, and high requirements. This review compares the qualitative differences of AXT derived from different natural sources, evaluates the upstream procedures for AXT expression in different chassis organisms, and investigates synthetic biology- and cell factory-based strategies for the industrial production of natural AXT. Synthetic biology is a promising novel strategy for reprogramming plants or microorganisms to produce AXT. Additionally, genetic engineering using cell factories extends beyond terrestrial applications, as it may contribute to the long-term sustainability of human health during space exploration and migration endeavors. This review provides a theoretical basis for the efficient and accurate genetic engineering of AXT from the microalga Haematococcuspluvialis, providing a valuable reference for future research on the biomanufacturing of AXT and other biological metabolites.

Alternative green solvents associated with ultrasound-assisted extraction: A green chemistry approach for the extraction of carotenoids and chlorophylls from microalgae

This study proposes a method for the ultrasonic extraction of carotenoids and chlorophyll from Scenedesmus obliquus and Arthrospira platensis microalgae with green solvents. Ethanol and ethanolic solutions of ionic liquids were tested with a variety of extraction parameters, including number of extractions, time of extraction, and solid-liquid ratio R(S/L), to determine the optimal conditions. After selecting the most effective green solvent (ethanol), the process conditions were established: R(S/L) of 1:10, three extraction cycles at 3 min each), giving an extraction yield of 2602.36 and 764.21 μgcarotenoids.gdried biomass-1; and 22.01 and 5.81 mgchlorophyll.gdried biomass-1 in S. obliquus and A. platensis, respectively. The carotenoid and chlorophyll extracts obtained using ethanol were shown to be potent scavengers of peroxyl radical, being 5.94 to 26.08 times more potent α-tocopherol. These findings pave the way for a green strategy for valorizing microalgal biocompounds through efficient and environmentally friendly technological processes.

Antioxidant Ready-to-Use Grape Pomace Extracts Recovered with Natural Eutectic Mixtures for Formulation of Color-Rich Gummies

The growing consumer demand for natural and eco-friendly food products motivates the development and evaluation of new and natural inputs for the food industry. So, this work explores the potential of grape pomace (GP) from winemaking, a food production residue, to obtain an anthocyanin-rich, ready-to-use extract with antioxidant activity that can confer improved color-rich gummy candies. The anthocyanins' chemical nature and the predictive COSMO-SAC model was considered for screening the best natural eutectic mixture for anthocyanin extraction. The eutectic mixtures composed of choline chloride as a hydrogen bond acceptor and acetic and citric acids as hydrogen bond donors were selected as solvents. The extraction was performed using a high-shear disperser (Ultra-Turrax®) at 45 °C and was stirred at 5000 rpm for 10 min. The extracts presented high total anthocyanin content (TAC), up to 60 µg equivalent of cyaniding-3-glucoside/g of dry GP, and high antioxidant activity as determined by DPPH and FRAP assays. The phenolic profile was also determined by high-performance liquid chromatography (HPLC) and the results corroborated with the antioxidant activity of the extracts. The results also demonstrate that eutectic mixtures enhance the extraction efficiency of anthocyanins and improve their stability, making them suitable for incorporation into functional food products such as gummies, acting as natural colorants.

Tailor-made solvents for microbial carotenoids recovery

In recent years, microbial carotenoids have emerged as a promising alternative for the pharmaceutical and food industries, particularly in promoting human health due to their potent antioxidant and antimicrobial properties. Microbial carotenoids, particularly those produced by yeast, bacteria, and microalgae, are synthesized intracellularly, requiring the use of solvents for their effective extraction and recovery. The conventional use of toxic volatile organic solvents (VOCs) like hexane, petroleum ether, and dimethyl sulfoxide in the extraction of microbial carotenoids has been common. However, ongoing research is introducing innovative, non-toxic, environmentally friendly tailor-made solvents, such as ionic liquids (IL) and deep eutectic solvents (DES), indicating a new era of cleaner and biocompatible technologies. This review aims to highlight recent advancements in utilizing IL and DES for obtaining carotenoids from microorganisms. Additionally, we explore the utilization of in silico tools designed to determine the solubilities of microbial carotenoids in tailor-made DES and ILs. This presents a promising alternative for the scientific community, potentially reducing the need for extensive experimental screening of solvents for the recovery of microbial carotenoids in the separation processing. According to our expert perspective, both IL and DES exhibit a plethora of exceptional attributes for the recovery of microbial carotenoids. Nevertheless, the current employment of these solvents for recovery of carotenoids is restricted to scientific exploration, as their feasibility for practical application in industrial settings has yet to be conclusively demonstrated. KEY POINTS: • ILs and DES share many tailoring properties for the recovery of microbial carotenoids • The use of ILs and DES for microbial carotenoid extraction remains driven by scientific curiosity. • The economic feasibility of ILs and DES is yet to be demonstrated in industrial applications.

Fungal Pigments: Carotenoids, Riboflavin, and Polyketides with Diverse Applications

Natural pigments and colorants have seen a substantial increase in use over the last few decades due to their eco-friendly and safe properties. Currently, customer preferences for more natural products are driving the substitution of natural pigments for synthetic colorants. Filamentous fungi, particularly ascomycetous fungi (Monascus, Fusarium, Penicillium, and Aspergillus), have been shown to produce secondary metabolites containing a wide variety of pigments, including β-carotene, melanins, azaphilones, quinones, flavins, ankaflavin, monascin, anthraquinone, and naphthoquinone. These pigments produce a variety of colors and tints, including yellow, orange, red, green, purple, brown, and blue. Additionally, these pigments have a broad spectrum of pharmacological activities, including immunomodulatory, anticancer, antioxidant, antibacterial, and antiproliferative activities. This review provides an in-depth overview of fungi gathered from diverse sources and lists several probable fungi capable of producing a variety of color hues. The second section discusses how to classify coloring compounds according to their chemical structure, characteristics, biosynthetic processes, application, and present state. Once again, we investigate the possibility of employing fungal polyketide pigments as food coloring, as well as the toxicity and carcinogenicity of particular pigments. This review explores how advanced technologies such as metabolic engineering and nanotechnology can be employed to overcome obstacles associated with the manufacture of mycotoxin-free, food-grade fungal pigments.

A review of natural astaxanthin production in a circular bioeconomy context using Paracoccus carotinifaciens

Astaxanthin (AXT) is a ketocarotenoid with several properties, including antioxidant, antidiabetic and anticancer with a wide range of applications in cosmeceutical, feed, food and pharmaceuticals sectors. The large fraction of AXT available in the market is obtained by chemical route, but the consumers preference for natural products are changing the global market of AXT, and due to that several companies are looking for potential alternative sources such as Gram-negative bacteria Paracoccus carotinifaciens (P. carotinifaciens) to obtain natural AXT. The aim of this critical review is to provide a comprehensive overview of the latest AXT research findings and characteristics of the hyperproducer-AXT P. carotinifaciens. Moreover, a brief description of the potential application of P. carotinifaciens for the production of natural AXT at industrial scale for commercial purposes and the latest advancements in the upstream and downstream procedures following the biorefinery and circular economy percepts are considered.

Development of Biotechnological Photosensitizers for Photodynamic Therapy: Cancer Research and Treatment-From Benchtop to Clinical Practice

Photodynamic therapy (PDT) is a noninvasive therapeutic approach that has been applied in studies for the treatment of various diseases. In this context, PDT has been suggested as a new therapy or adjuvant therapy to traditional cancer therapy. The mode of action of PDT consists of the generation of singlet oxygen (¹O₂) and reactive oxygen species (ROS) through the administration of a compound called photosensitizer (PS), a light source, and molecular oxygen (³O₂). This combination generates controlled photochemical reactions (photodynamic mechanisms) that produce ROS, such as singlet oxygen (¹O₂), which can induce apoptosis and/or cell death induced by necrosis, degeneration of the tumor vasculature, stimulation of the antitumor immune response, and induction of inflammatory reactions in the illuminated region. However, the traditional compounds used in PDT limit its application. In this context, compounds of biotechnological origin with photosensitizing activity in association with nanotechnology are being used in PDT, aiming at its application in several types of cancer but with less toxicity toward neighboring tissues and better absorption of light for more aggressive types of cancer. In this review, we present studies involving innovatively developed PS that aimed to improve the efficiency of PDT in cancer treatment. Specifically, we focused on the clinical translation and application of PS of natural origin on cancer.