Evaluating the economic viability and environmental impact of emerging technologies is crucial for the transition to a bio-based economy. This study proposes a methodology to assess the environmental and economic performance of bio-based lactic acid (LA) production by scaling up from pilot to industrial levels using fiber sludge, a residue from the pulp and paper industry, as a feedstock. Process design, Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA) were conducted at pilot scale to identify key environmental and economic hotspots. External costs were estimated following the environmental Life Cycle Costing (eLCC) approach using the Environmental Prices (EP) method. At the pilot scale, the LCA indicated a Global Warming Potential (GWP) of 3.87 kg CO₂-eq, which aligns with the values reported in previous studies. Scaling up to different plant capacities revealed the potential economies of scale. At a production rate of 50 kt per year, the Minimum Selling Price (MSP) was estimated at 1.71€/kg, which is comparable to that of other bio-based LA production routes. Assuming proportional environmental impacts from pilot to industrial scale, external costs were integrated into the MSP, resulting in adjusted values of 2.04€/kg (lower value), 2.21€/kg (central value), and 2.46 €/kg (upper value). Sensitivity and uncertainty analyses using Monte Carlo simulations indicated an 87.5 % probability of achieving a positive Net Present Value (NPV). This study highlights the need for standardised methodologies to evaluate the environmental and economic impacts of emerging bio-based technologies, particularly when accounting for external costs

The utilization of a cheap side stream is the core for biotechnological production of platform chemicals, such as, succinic acid. This study explores lab and pilot scale fermentation of Actinobacillus succinogenes (B1) and Basfia succiniciproducens (B2) to produce succinic acid from sulphide fibre sludge, a side product from pulp and paper industry. Both strains demonstrated efficient SA production, with lag phase of 2–3 h, accompanied by by-product formation of formic acid (FA) and acetic acid (AA). B1 outperformed B2 in SA concentration (28.4 g∙L-1 vs 20.4 g∙L-1) and yield ( 0.76 g·g-1 and 0.51 g·g-1), leading to its selection for pilot scale fermentations. Pilot scale fermentations using SFS hydrolysate as carbon source achieved SA yields of 0.62–0.66 g/g with productivities of 0.65 – 0.78 g∙L-1 SA. SFS hydrolysate, rich in glucose provided a promising substrate, yielding 23 g∙L-1 SA. Two downstream processing (DSP) methds were evaluated for SA recovery. DSP 1, involving microfiltration, electrodialysis, and ion exchange, achieved 62 % recovery but incurred losses during filtration and electrodialysis. DSP2 utilized activated carbon for decolorization, followed by microfiltration and crystallization, yielding 60.3 % SA recovery. Both DSP approaches produced high purity SA suitable for polymer applications. These results underscore the potential of SFS hydrolysate for sustainable SA production and highlight the need for process optimization, including fed-batch or continuous systems, to enhance yields and reduce costs. These findings contribute to advancing biobased monomer production as a viable alternative to fossil-based methods. 

Carbonic anhydrase (CA) is considered an efficient enzyme for fermentation systems exhibiting a wide range of applications, enhancing both the efficacy and output of the fermentation process. The present study aimed to evaluate the production of acidogenic biohydrogen (bioH2) and volatile fatty acids (VFA) using forest residues as a renewable feedstock. Specifically, the study examined the integration of CA derived from Desulfovibrio vulgaris into the acidogenic fermentation (AF) process. The experimental procedure involved a cascade design conducted in two distinct phases. In phase I, the concentration of CA in the AF was systematically optimized, with glucose serving as the substrate. In phase II, three influential parameters (pH, pressurization with in situ generated gas and organic load) were evaluated on AF in association with optimized CA concentration from phase I. In phase II, glucose was replaced with renewable sugars obtained from forest residues after steam explosion pretreatment followed by enzymatic saccharification. The incorporation of CA in AF was found to be beneficial in steering acidogenic metabolites. Alkaline conditions (pH 8) promoted bioH2, yielding 210.9 mLH2 gCOD−1, while introducing CA further increased output to 266.6 mLH2 gCOD−1. This enzymatic intervention improved the production of bioH2 conversion efficiency (HCE) from 45.3% to 57.2%. Pressurizing the system accelerated VFA production with complete utilization of in situ produced H2 + CO2 compared to non-pressurized systems. Particularly, caproic acid production was improved under pressurized conditions which was accomplished by the targeted enrichment of chain-elongating bacteria in the mixed culture. The microbial diversity analysis showed the dominance of Firmicutes suggesting a significant degree of adaptation to the experimental contexts, leading to an enhanced production of acidogenic metabolites. 

The effective and cheap production of platform chemicals is a crucial step towards the transition to a bio-based economy. In this work, biotechnological methods using sustainable, cheap, and readily available raw materials bring bio-economy and industrial microbiology together: Microbial production of two platform chemicals is demonstrated [lactic (LA) and succinic acid (SA)] from a non-expensive side stream of pulp and paper industry (fibre sludge) proposing a sustainable way to valorize it towards economically important monomers for bioplastics formation. This work showed a promising new route for their microbial production which can pave the way for new market expectations within the circular economy principles. Fibre sludge was enzymatically hydrolysed for 72 h to generate a glucose rich hydrolysate (100 g·L−1 glucose content) to serve as fermentation medium for Bacillus coagulans A 541, A162 strains and Actinobacillus succinogenis B1, as well as Basfia succiniciproducens B2. All microorganisms were investigated in batch fermentations, showing the ability to produce either lactic or succinic acid, respectively. The highest yield and productivities for lactic production were 0.99 g·g−1 and 3.75 g·L−1·h−1 whereas the succinic acid production stabilized at 0.77 g·g−1 and 1.16 g·L−1·h−1. Copyright © 2023 Olszewska-Widdrat, Xiros, Wallenius, Schneider, Rios da Costa Pereira and Venus.

The demand for cheap, healthy, and sustainable alternative protein sources has turned research interest into microbial proteins. Mycoproteins prevail due to their quite balanced amino acid profile, low carbon footprint and high sustainability potential. The goal of this research was to investigate the capability of Pleurotus ostreatus to metabolize the main sugars of agro-industrial side streams, such as aspen wood chips hydrolysate, to produce high-value protein with low cost. Our results indicate that P. ostreatus LGAM 1123 could be cultivated both in a C-6 (glucose)- and C-5(xylose)-sugar-containing medium for mycoprotein production. A mixture of glucose and xylose was found to be ideal for biomass production with high protein content and rich amino acid profile. P. ostreatus LGAM 1123 cultivation in a 4 L stirred-tank bioreactor using aspen hydrolysate was achieved with 25.0 ± 3.4 g L−1 biomass production, 1.8 ± 0.4 d−1 specific growth rate and a protein yield of 54.5 ± 0.5% (g/100 g sugars). PCA analysis of the amino acids revealed a strong correlation between the amino acid composition of the protein produced and the ratios of glucose and xylose in the culture medium. The production of high-nutrient mycoprotein by submerged fermentation of the edible fungus P. ostreatus using agro-industrial hydrolysates is a promising bioprocess in the food and feed industry. © 2023 by the authors.

Agricultural land shrinkage, decreasing global water resources, population increase and malnutrition highlight the need for new food sources. Single-cell protein derived from microorganisms could be a solution to high protein demand. The aim of this work was to optimize the cultivation conditions for single-cell protein production by Pleurotus ostreatus LGAM 1123 in submerged cultures and valorize fiber sludge, a low cost industrial side stream from the pulp and paper industry, as a substrate for single-cell protein (SCP) production. A study on the effect of different cultivation conditions on fungal growth and protein production has been conducted. Response surface methodology was used to investigate the combined effect of the most important factors (glucose and yeast extract medium concentrations) and optimize the process. A maximum protein production of 10.0 ± 0.9 g L-1 was found for the submerged cultivation of the fungus in a 3.5 L stirred-tank bioreactor, while the biomass produced and its total protein content were 26.0 ± 2.0 g L-1 and 44.8 ± 0.8%, respectively. As an industrial application, a cellulosic hydrolysate obtained after enzymatic hydrolysis of fibre sludge in the optimized medium composition was used. Fibre sludge was shown to be an excellent feedstock for SCP production achieving productivity and protein content very similar to glucose fermentations. Single-cell protein of P. ostreatus presented higher amino acid scores compared to the recommended ones for valine, leucine, and aromatic amino acids in human nutrition. Therefore, P. ostreatus biomass could stand as an alternative vegan protein source due to its high protein content and amino acid composition. 

The ability of the multispecies biofilm membrane reactors (MBM reactors) to provide distinguished niches for aerobic and anaerobic microbes at the same time was used for the investigation of the consolidated bioprocessing of cellulose to short chain fatty acids (SCFAs). A consortium based consolidated bioprocess (CBP) was designed. The rumen microbiome was used as the converting microbial consortium, co-cultivated with selected individual aerobic fungi which formed a biofilm on the tubular membrane flushed with oxygen. The beneficial effect of the fungal biofilm on the process yields and productivities was attributed to the enhanced cellulolytic activities compared with those achieved by the rumen microbiome alone. At 30 °C, the MBM system with Trichoderma reesei biofilm reached a concentration 39% higher (7.3 g/L SCFAs), than the rumen microbiome alone (5.1 g/L) using 15 g/L crystalline cellulose as the substrate. Fermentation temperature was crucial especially for the composition of the short chain fatty acids produced. The temperature increase resulted in shorter fatty acids produced. While a mixture of acetic, propionic, butyric, and caproic acids was produced at 30 °C with Trichoderma reesei biofilm, butyric and caproic acids were not detected during the fermentations at 37.5 °C carried out with Coprinopsis cinerea as the biofilm forming fungus. Apart from the presence of the fungal biofilm, no parameter studied had a significant impact on the total yield of organic acids produced, which reached 0.47 g of total SCFAs per g of cellulose (at 30 °C and at pH 6, with rumen inoculum to total volume ratio equal to 0.372).

In this paper, two ethanol processes integrated with a softwood pulp mill are compared with regard to their steam demand, process integration potential and profitability. The processes differ in the solids loading in the simultaneous saccharification and fermentation step and in the resulting ethanol concentration. The results show that a higher ethanol concentration does not necessarily lead to significant reductions in steam demand. Instead, it is demonstrated that the steam demand for distillation is highly dependent on the design of the distillation plant. Nevertheless, a higher solids loading (high gravity) can be beneficial for the treatment of the stillage from the distillation plant. A higher solids loading results either in a lower steam demand for evaporation of the stillage or possibly in a reduced demand for effluent treatment compared to a conventional solids loading process. While the results show that a higher ethanol concentration leads to advantages in energy costs and investment costs for the distillation plant, they also show that the potential benefits of a high-gravity process are offset by the expected decrease in ethanol yield, which leads to higher raw material costs.

Background: Lignocellulosic materials are a diverse group of substrates that are generally scarce in nutrients, which compromises the tolerance and fermentation performance of the fermenting organism. The problem is exacerbated by harsh pre-treatment, which introduces sugars and substances inhibitory to yeast metabolism. This study compares the fermentation behaviours of two yeast strains using different types of lignocellulosic substrates; high gravity dilute acid spruce hydrolysate (SH) and spent sulphite liquor (SSL), in the absence and presence of yeast extract. To this end, the fermentation performance, energy status and fermentation capacity of the strains were measured under different growth conditions.Results: Nutrient supplementation with yeast extract increased sugar uptake, cell growth and ethanol production in all tested fermentation conditions, but had little or no effect on the energy status, irrespective of media. Nutrient-supplemented medium enhanced the fermentation capacity of harvested cells, indicating that cell viability and reusability was increased by nutrient addition.Conclusions: Although both substrates belong to the lignocellulosic spruce hydrolysates, their differences offer specific challenges and the overall yields and productivities largely depend on choice of fermenting strain.