Activated charcoal and microfiltration as pretreatment before ultrafiltration of pectinases produced by Aspergillus niger in solid-state cultivation

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.

Membrane processes for environmental remediation of nanomaterials: Potentials and challenges

Nanomaterials have gained huge attention with their wide range of applications. This is mainly driven by their unique properties. Nanomaterials include nanoparticles, nanotubes, nanofibers, and many other nanoscale structures have been widely assessed for improving the performance in different applications. However, with the wide implementation and utilization of nanomaterials, another challenge is being present when these materials end up in the environment, i.e. air, water, and soil. Environmental remediation of nanomaterials has recently gained attention and is concerned with removing nanomaterials from the environment. Membrane filtration processes have been widely considered a very efficient tool for the environmental remediation of different pollutants. Membranes with their different operating principles from size exclusions as in microfiltration, to ionic exclusion as in reverse osmosis, provide an effective tool for the removal of different types of nanomaterials. This work comprehends, summarizes, and critically discusses the different approaches for the environmental remediation of engineered nanomaterials using membrane filtration processes. Microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) have been shown to effectively remove nanomaterials from the air and aqueous environments. In MF, the adsorption of nanomaterials to membrane material was found to be the main removal mechanism. While in UF and NF, the main mechanism was size exclusion. Membrane fouling, hence requiring proper cleaning or replacement was found to be the major challenge for UF and NF processes. While limited adsorption capacity of nanomaterial along with desorption was found to be the main challenges for MF.

From the culture broth to the erythritol crystals: an opportunity for circular economy

Abstract

The reduction of sugar intake by adults has been stated by the World Health Organization as an important strategy to reduce the risk of non-communicable diseases. Erythritol is a four-carbon sugar alcohol that is considered as a highly suitable substitution for sucrose. This review article covers approaches for the separate stages of the biotechnological production of erythritol from cultivation to the downstream section. The first part focuses on the cultivation stage and compares the yields of erythritol and arising by-products achieved with different types of substrates (commercial versus alternative ones). The reported numbers obtained with the most prominently used microorganisms in different cultivation methods (batch, fed-batch or continuous) are presented. The second part focuses on the downstream section and covers the applied technologies for cell removal, recovery, purification and concentration of erythritol crystals, namely centrifugation, membrane separation, ion and preparative chromatography, crystallization and drying. The final composition of the culture broth and the preparative chromatography separation performance were identified as critical points in the production of a high-purity erythritol fraction with a minimum amount of losses. During the review, the challenges for a biotechnological production of erythritol in a circular economy context are discussed, in particular regarding the usage of sustainable resources and minimizing waste streams.

Key points

• Substitution of sucrose by erythritol can be a step towards a healthier society

• Biotechnological production of erythritol should follow a circular economy concept

• Culture broth composition and preparative chromatography are keys for downstreaming

• Substrate, mother liquor and nutrients are challenges for circular economy

Simultaneous cellulase production using domestic wastewater and bioprocess effluent treatment - A biorefinery approach

The production of cellulases using domestic wastewater as an alternative culture medium and reducing the pollutant charge of the resultant effluents were assessed for the first time in this study. Cellulase production was carried out in a bubble column, column-packed bed and stirred tank reactors by Trichoderma harzianum. Maximum cellulase activity and productivity of 31 U_FP/mL and 645 U_FP/mL.h, respectively were achieved in the bubble column bioreactor system without immobilization. The fermented broth was microfiltrated and ultrafiltrated, leading to a cellulase recovery of 73.5% using a 30 kDa membrane and resulting in a 4.23-fold activity concentration. Chemical oxygen demand and nitrogen concentration were reduced 81.37% and 52.9%, respectively, showing great promise in producing cellulases using domestic wastewater with concomitant development of a medium- to-high added-value process and reduced environmental impact. These results contribute to the development of sustainable bioprocesses approaching a biorefinery concept.

Bioreactors in solid state fermentation technology: Design, applications and engineering aspects

In recent years, substantial credibility in employing Solid-State Fermentation (SSF) technique has been witnessed owing to its numerous advantages over submerged fermentation (SmF). In spite of enormous advantages, true potential of SSF technology has not been fully realized at industrial scale. The lack of rational and scalable bioreactor designs backed by mathematical models and automated control system that could successfully address heterogeneity with respect to heat and mass, and also operate aseptically, remains the prime reason for it. As a result, there still exists vast scope in SSF bioreactor research and development to facilitate broad spectrum of biotechnological applications. The present article reviews state-of-the-art in SSF technology with focus on bioreactors that have been employed for bioprocess applications, in particular, enzyme production. Based on the mode of operation, bioreactors are divided into four categories with emphasis on design features, effect of operating conditions on productivity, applications and limitations. Selected modeling studies developed over the years, have been revised and presented in problem specific manner in order to address the limitations. Some interesting designs including few recent ones that have been proposed and/or employed at pilot and industrial levels are discussed in more detail.