Recent Advances in Miscanthus Macromolecule Conversion: A Brief Overview

Miscanthus is a valuable renewable feedstock and has a significant potential for the manufacture of diverse biotechnology products based on macromolecules such as cellulose, hemicelluloses and lignin. Herein, we overviewed the state-of-the art of research on the conversion of miscanthus polymers into biotechnology products comprising low-molecular compounds and macromolecules: bioethanol, biogas, bacterial cellulose, enzymes (cellulases, laccases), lactic acid, lipids, fumaric acid and polyhydroxyalkanoates. The present review aims to assess the potential of converting miscanthus polymers in order to develop sustainable technologies

Miscanthus × Giganteus var. KAMIS as a New Feedstock for Cellulose Nitrates

В связи с ограниченностью объемов традиционных источников целлюлозы (хлопка и древесины) исследования, направленные на получение наиболее конкурентоспособных наукоемких продуктов – нитратов целлюлозы – из нового отечественного нетрадиционного легковозобновляемого сырья, чрезвычайно актуальны. Анализ источников научной информации подтверждает отсутствие данных о возможности получения нитратов целлюлозы из мискантуса за исключением публикаций авторов. В данной работе в качестве перспективного сырьевого источника предложена древовидная техническая злаковая культура – мискантус гигантский сорта «КАМИС», произрастающий с урожайностью до 20 т/га в год на агропромышленных плантациях в Калининградской, Калужской, Брянской, Ярославской областях и в Приморском крае. Образец технической целлюлозы, выделенный азотнокислым способом из мискантуса сорта «КАМИС», характеризуется высокими значениями массовой доли α-целлюлозы – 96 % и степени полимеризации – 1350. В установленных ранее для нетрадиционного сырья оптимальных условиях синтеза путем обработки технической целлюлозы промышленно доступной серно-азотной кислотной смесью был получен образец нитратов целлюлозы с основными функциональными свойствами: массовая доля азота 11,26 %, вязкость 52 мПа∙с, растворимость в спиртоэфирной смеси 95 %. Методом растровой электронной микроскопии охарактеризованы морфологические особенности образцов технической целлюлозы и нитратов целлюлозы. Методом ИК-спектроскопии выявлено наличие основных функциональных групп в образцах технической целлюлозы (3411, 2913, 1637, 1429, 1369, 1317, 1161, 700-500 см-1) и нитратов целлюлозы (2553, 1642, 1276, 830, 746, 680 см-1), позволяющих идентифицировать их как целлюлозу и азотнокислые эфиры целлюлозы соответственно. Методом дифференциальной сканирующей калориметрии установлено, что по температуре начала интенсивного разложения (199 °С) и удельной теплоте разложения (8,43 кДж/г) образец нитратов целлюлозы соответствует промышленным коллоксилинам. Практическая значимость работы заключается в экспериментальном обосновании возможности использования нового отечественного нетрадиционного легковозобновляемого сырья – мискантуса сорта «КАМИС» в качестве прекурсора нитратов целлюлозы высокого качестваDue to the limited volumes of conventional sources of cellulose (cotton and wood), research centered on producing the most competitive science-driven products – cellulose nitrates – from new, domestic, easily renewable feedstocks is extremely relevant. The review of scientific literature corroborates the lack of data on the feasibility to obtain cellulose nitrates from Miscanthus, except for the authors’ publications. Here we suggest a tree-like industrial crop, Miscanthus var. KAMIS, growing with an yield of up to 20 t/ha a year on industrial plantations in Kaliningradskaya, Kaluzhskaya and Yaroslavskaya Oblasts and in Primorskiy Krai. A pulp sample derived from Miscanthus var. KAMIS by the nitric-acid process exhibits a high α-cellulose content of 96 % and degree of polymerization of 1350. Under optimum synthesis conditions previously identified for unconventional feedstocks, a cellulose nitrate sample was synthesized by treating the pulp with commercially available mixed acid and had the following functional characteristics: 11.26 % nitrogen content, 52 mPа∙s viscosity, and – 95 % solubility on alcohol-ester mixture. Morphological features of pulp and cellulose nitrate samples were characterized by scanning electron microscopy. IR spectroscopy revealed the presence of functional groups in pulp samples (3411, 2913, 1637, 1429, 1369, 1317, 1161, 700-500 cm-1) and cellulose nitrate samples (2553, 1642, 1276, 830, 746, 680 cm-1), which allow those samples to be identified as cellulose and nitrate cellulose esters, respectively. It was found by scanning electron microscopy that the cellulose nitrate sample matches industrial Colloxylines by the onset temperature of decomposition (199 °С) and specific head of decomposition (8,43 kJ/g). The practical importance of this study is that we experimentally justify the feasibility to utilize the new, unconventional, domestic, easily renewable feedstock, Miscanthus var. KAMIS, as a precursor of high-quality cellulose nitrate

Evaluation of Chemical Composition of Miscanthus × giganteus Raised in Different Climate Regions in Russia

Lignocellulosic biomass is of great interest as an alternative energy resource because it offers a range of merits. Miscanthus × giganteus is a lignocellulosic feedstock of special interest, as it combines a high biomass productivity with a low environmental impact, including CO2 emission control. The chemical composition of lignocellulose determines the application potential for efficient industrial processing. Here, we compiled a sample collection of Miscanthus × giganteus that had been cultivated in different climate regions between 2019 and 2021. The chemical composition was quantified by the conventional wet methods. The findings were compared with each other and with the known data. Starting as soon as the first vegetation year, Miscanthus was shown to feature the following chemical composition: 43.2–55.5% cellulose content, 17.1–25.1% acid-insoluble lignin content, 17.9–22.9% pentosan content, 0.90–2.95% ash content, and 0.3–1.2% extractives. The habitat and the surrounding environment were discovered herein to affect the chemical composition of Miscanthus. The stem part of Miscanthus was found to be richer in cellulose than the leaf (48.4–54.9% vs. 47.2–48.9%, respectively), regardless of the planation age and habitat. The obtained findings broaden the investigative geography of the chemical composition of Miscanthus and corroborate the high value of Miscanthus for industrial conversion thereof into cellulosic products worldwide

Biosynthesis of Bacterial Cellulose by Extended Cultivation with Multiple Removal of BC Pellicles

Extended cultivation with multiple removal of BC pellicles is proposed herein as a new biosynthetic process for bacterial cellulose (BC). This method enhances the BC surface area by 5–11 times per unit volume of the growth medium, improving the economic efficiency of biosynthesis. The resultant BC gel-films were thin, transparent, and congruent. The degree of polymerization (DP) and elastic modulus (EM) depended on the number of BC pellicle removals, vessel shape, and volume. The quality of BC from removals II–III to VII was better than from removal I. The process scale-up of 1:40 by volume increased DP by 1.5 times and EM by 5 times. A fact was established that the symbiotic Medusomyces gisevii Sa-12 was adaptable to exhausted growth medium: the medium was able to biosynthesize BC for 60 days, while glucose ran low at 24 days. On extended cultivation, DP and EM were found to decline by 39–64% and 57–65%, respectively. The BC gel-films obtained upon removals I–VI were successfully trialed in experimental tension-free hernioplasty

Static Culture Combined with Aeration in Biosynthesis of Bacterial Cellulose

One of the ways to enhance the yield of bacterial cellulose (BC) is by using dynamic aeration and different-type bioreactors because the microbial producers are strict aerobes. But in this case, the BC quality tends to worsen. Here we have combined static culture with aeration in the biosynthesis of BC by symbiotic Medusomyces gisevii Sa-12 for the first time. A new aeration method by feeding the air onto the growth medium surface is proposed herein. The culture was performed in a Binder-400 climate chamber. The study found that the air feed at a rate of 6.3 L/min allows a 25% increase in the BC yield. Moreover, this aeration mode resulted in BC samples of stable quality. The thermogravimetric and X-ray structural characteristics were retained: the crystallinity index in reflection and transmission geometries were 89% and 92%, respectively, and the allomorph Iα content was 94%. Slight decreases in the degree of polymerization (by 12.0% compared to the control―no aeration) and elastic modulus (by 12.6%) are not critical. Thus, the simple aeration by feeding the air onto the culture medium surface has turned out to be an excellent alternative to dynamic aeration. Usually, when the cultivation conditions, including the aeration ones, are changed, characteristics of the resultant BC are altered either, due to the sensitivity of individual microbial strains. In our case, the stable parameters of BC samples under variable aeration conditions are explained by the concomitant factors: the new efficient aeration method and the highly adaptive microbial producer―symbiotic Medusomyces gisevii Sa-12