TECHNOLOGY AND EQUIPMENT FOR PROCESSING ACTIVATED AGRICULTURAL PLANT WASTE INTO BIOETHANOL

The article is devoted to the development of technology and equipment for the production of bioethanol from agricultural plant waste, activated by the steam explosion method. The value and novelty of research lies in obtaining new data on the effective acidic and enzymatic hydrolysis of activated raw materials, and developing a technology for the conversion of plant raw materials into bioethanol. The studies were carried out on the basis of the Department of Wood Materials Processing of Kazan National Research Technological University (Republic of Tatarstan, Kazan). A pilot plant for the production of bioethanol and the principle of its operation are presented. Pine wood waste and wheat straw (collected in Kukmor region of the Republic of Tatarstan in the period August-September 2021) were used as raw materials. Steam-explosive activation of raw materials was carried out at temperatures of 165 ⁰C and 210 ⁰C for 5 minutes. Acid hydrolysis parameters: H2SO4 concentration - 0.5% and 1.5%, hydromodule 1:15, hydrolysis temperature - 187⁰C, hydrolysis duration - 5 hours. Enzymatic hydrolysis parameters: preparation - Cellulox-A (OOO PO Sibbiopharm, Russia) - 6 and 12 g/kg of raw material, hydrolysis temperature - 45 ⁰C, substrate pH 4.7 (acetate buffer), raw material concentration in the substrate 33 g/l, the duration of hydrolysis is 72 h. Alcoholic fermentation of hydrolysates was carried out at 32-34⁰C using Saccharomyces cerevisiae yeast, fermentation duration 7 h, yeast concentration 25 g/l. The bioethanol yield in % of reducing substances was recalculated after determining the mass yield. It is concluded that the vapor-explosive activation of pine wood at a temperature of 210 ºC makes it possible to obtain by acid hydrolysis and anaerobic fermentation of reducing substances up to 0.26 kg (0.33 l) of ethanol from 1 kg of activated raw materials, and activation of wheat straw at the same temperature allows obtaining up to 0.172 kg (0.218 l) ethanol with 1 kg of activated straw

Effect of simultaneous use of microwave and ultrasound irradiations on the sulfuric acid hydrolysis lignin (SAHL) depolymerization

In this study, the individual and combined effect of microwave (MW) and ultrasound (US) processes on the depolymerization of sulfuric acid hydrolysis lignin (SAHL) was investigated in a hybrid microwave–ultrasound...

Solid Acid Hydrolysis for Isolation of Cellulose Nanocrystals and Chitin Nanocrystals – A mini review

Cellulose and chitin are two of the most abundant biopolymer on earth, have been attracted a lot of interest from many researchers, especially related to their nanoparticles form. Recently the method to extract them into nanoscale materials mostly by mineral or liquid acid hydrolysis, such as sulfuric and hydrochloric acid. Despite their high yield production, many disadvantages are produced by their use as a hydrolysis catalyst, such as low thermal stability and are difficult to be functionalized due to the presence of sulfate groups, tendency to be aggregated due to the bare surface charge density, the potential excessive degradation of cellulose; and large amounts of effluent will be produced due to the neutralization stage and corrosion hazards to the equipment and environment. To overcome the drawback of those acids, solid acid can be used to produce cellulose (CNC) and chitin nanocrystals (ChNC). Their ability to recrystallize and recycle makes them more environmentally friendly, furthermore, most of the acid can do esterification on the surface of cellulose and chitin. The purpose of this paper is to provide a critical review of recent progress related to solid acid hydrolysis since they have interesting characterization even some of their attribute is better than the conventional method.

Production and Properties of Microbial Polyhydroxyalkanoates Synthesized from Hydrolysates of Jerusalem Artichoke Tubers and Vegetative Biomass

One of the major challenges in PHA biotechnology is optimization of biotechnological processes of the entire synthesis, mainly by using new inexpensive carbon substrates. A promising substrate for PHA synthesis may be the sugars extracted from the Jerusalem artichoke. In the present study, hydrolysates of Jerusalem artichoke (JA) tubers and vegetative biomass were produced and used as carbon substrate for PHA synthesis. The hydrolysis procedure (the combination of aqueous extraction and acid hydrolysis, process temperature and duration) influenced the content of reducing substances (RS), monosaccharide contents, and the fructose/glucose ratio. All types of hydrolysates tested as substrates for cultivation of three strains—C. necator B-10646 and R. eutropha B 5786 and B 8562—were suitable for PHA synthesis, producing different biomass concentrations and polymer contents. The most productive process, conducted in 12-L fermenters, was achieved on hydrolysates of JA tubers (X = 66.9 g/L, 82% PHA) and vegetative biomass (55.1 g/L and 62% PHA) produced by aqueous extraction of sugars at 80 °C followed by acid hydrolysis at 60 °C, using the most productive strain, C. necator B-10646. The effects of JA hydrolysates on physicochemical properties of PHAs were studied for the first time. P(3HB) specimens synthesized from the JA hydrolysates, regardless of the source (tubers or vegetative biomass), hydrolysis conditions, and PHA producing strain employed, exhibited the 100–120 °C difference between the Tmelt and Tdegr, prevailing of the crystalline phase over the amorphous one (Cx between 69 and 75%), and variations in weight average molecular weight (409–480) kDa. Supplementation of the culture medium of C. necator B-10646 grown on JA hydrolysates with potassium valerate and ε-caprolactone resulted in the synthesis of P(3HB-co-3HV) and P(3HB-co-4HB) copolymers that had decreased degrees of crystallinity and molecular weights, which influenced the porosity and surface roughness of polymer films prepared from them. The study shows that JA hydrolysates used as carbon source enabled productive synthesis of PHAs, comparable to synthesis from pure sugars. The next step is to scale up PHA synthesis from JA hydrolysates and conduct the feasibility study. The present study contributes to the solution of the critical problem of PHA biotechnology—finding widely available and inexpensive substrates.

In vitro Prebiotic Properties of Garlic Polysaccharides and Its Oligosaccharide Mixtures Obtained by Acid Hydrolysis

Fructans and oligofructose are usually used as prebiotics without any limitation in functional food or food ingredients. The degree of polymerization (DP) of polysaccharides affects the utilization of probiotics. Garlic is rich in fructans. The objective of this study was to extract and purify polysaccharides from garlic, analyze its composition, hydrolyze them using HCl, and then evaluate the prebiotic potential of the garlic neutral polysaccharides (GPs) before and after hydrolysis. GPs were 6.57 × 103 Da with a composition of fructose and glucose at a ratio of 4:1. After acid hydrolysis, low molecular weight fraction in garlic oligofructose (GOs) may be eliminated through ultrafiltration. The content of oligosaccharides with an average DP < 10 increased from 15 to 75%. GPs and GOS had a stronger resistance to acid conditions in human stomach than fructooligosaccharide, and GOs showed better prebiotic properties on the growth of lactobacilli than GPs. This study evaluates the prebiotic potential of the garlic frutctans and oligosaccharides mixtures obtained by acid hydrolysis, which may be used as an ingredient in functional food and nutraceutical products.

Acid hydrolysis of spent coffee grounds: effects on possible prebiotic activity of oligosaccharides

Background Spent coffee grounds (SCG) are a promising source of natural by-products which can be used for different purposes. In this work, a possible use of oligosaccharides isolated from SCG as functional ingredients was investigated. SCGs were treated with an acid hydrolysis at high temperature (200 °C) in a closed reactor setting reaction time of 30, 60 and 90 s depending on the sample (original or defatted). A comprehensive study of the resulted water-soluble hydrolysate using a high-resolution mass spectrometry analysis was performed. Additionally, the growth of four Lactobacillus strains was tested to assess the prebiotic potential of the hydrolysate. Results Oligosaccharide chains formed by hexoses with a degree of polymerization ranging from 3 to 6 were identified and characterized. Regardless of the composition and the reaction time of hydrolysis, the bacterial activity of SCG extracts exhibited significantly higher values than the well-known versatile carbohydrate used by food industry, i.e., inulin. Conclusions The results pave the way toward the use of hydrolysate SCG as an innovative ingredient intended to fortify food formulations. The diversity in coffee oligosaccharides composition suggests their selective prebiotic activity for specific bacterial strains. Graphical Abstract