Exploitation of Wheat Straw Biorefinery Side Streams as Sustainable Substrates for Microorganisms: A Feasibility Study

Abstract

Lignocellulosic agricultural side products, like wheat straw, are widely seen as an important contribution to a future sustainable economy. However, optimization of biorefinery processes and exploitation of all side streams are crucial for an economically viable biorefinery. Pretreatment of lignocellulosic raw material, which is necessary for further processing steps, can generate low-value side streams. In this feasibility study, side streams from a liquid hot water (LHW) pretreatment of wheat straw were utilized for the production of polyhydroxybutyrate (PHB) and highly valuable tetraether lipids (TELs). Additional value created by these products can benefit the biorefinery's economic operation. The utilized wheat straw was pretreated at 120 • C and 170 • C for up to two hours in laboratory and lab scale. The resulting side stream consists mainly of carbohydrates from hemicelluloses and fermentation inhibitors such as acetic acid. In order to achieve a successful production of both products, an acetic acid separation via distillation was necessary. Subsequently, the acetic acid fraction was utilized for the PHB production using cyanobacteria. The carbohydrate-rich fraction was applied in the cultivation of Sulfolobus acidocaldarius and resulted in the successful production of TELs. Both fractions achieved better fermentation yields compared to their corresponding reference media.

Modelling and Environmental Profile Associated with the Valorization of Wheat Straw as Carbon Source in the Biotechnological Production of Manganese Peroxidase

“…Among the different options of renewable raw materials that can be used as a resource for the biotechnological production of MnP, the use of wheat straw was considered for two main reasons: availability and molecular composition [44][45][46]. The production of wheat to meet consumer demands leads to the generation of large amounts of lignocellulosic residues, mainly wheat straw.…”

Integral Analysis of Liquid-Hot-Water Pretreatment of Wheat Straw: Evaluation of the Production of Sugars, Degradation Products, and Lignin

“…Instead, the hydrolysate could be used for fermentation with microorganisms metabolizing monomeric and oligomeric sugars. Some studies have been carried out to produce, e.g., polyhydroxybutyrate and tetraether lipids [18,28]. In this context, three of the studied conditions reached similar levels of total sugars to be potentially used, namely, 160 • C for 90 min, 180 • C for 30 min, and 180 • C for 60 min.…”

Bioconversion of Furanic Compounds by Chlorella vulgaris—Unveiling Biotechnological Potentials

“…Detoxification of so-called fermentation inhibitors, HMF, FF, and phenolic compounds is crucial to designing feasible processes, as yields and microbial growth are retarded by their presence. Detoxification processes can include lime addition [ 8 ], activated carbon resins [ 10 ], distillation [ 11 , 12 ], or organic solvent extraction [ 13 ]. However, chemical and mechanical strategies often lead to losses in monomeric sugar content and are energy- and time-intensive.…”