Smiltsērkšķu lignocelulozes biomasas bezatlikuma izmantošanas izpēte ilgtspējīgai multifunkcionālo produktu ražošanai: promocijas darba kopsavilkums zinātnes doktora grāda zinātnes doktors (Ph.D.) inženierzinātnēs un tehnoloģijās iegūšanai = Research on the zero-waste uses of sea buckthorn lignocellulosic biomass for sustainable manufacturing of multifunctional products: Summary of the doctoral thesis for the doctoral degree of science (Ph.D.) in engineering science and technology

Sea buckthorn belongs to prolific, quite ancient fruit species, whose fruits contain practically all vitamins found in nature. As a result of annual agrotechnical measures, a large volume of cut sea buckthorn branches is formed every year during seasonal pruning of sea buckthorn or harvesting of berries, which are burned currently without using their potential as a raw material for the production of biologically active substances and ecologically safe products/ preparations. The full and rational use of branches as lignocellulosic biomass into products with added value is one of the conditions for the sustainable use of renewable resources, promoting the growth of the national economy, increasing the productivity of local renewable resources and ensuring their stable use for industrial purposes, without harming the environment and human health. The introduction of herbal products into the market and the interest in them is constantly increasing, based on the demand for natural products in healthcare, pharmaceuticals, and even agriculture, such as for the extraction of plant protection products. Sea buckthorn lignocellulosic biomass contains various biologically active substances, including polyphenolic compounds and serotonin with multifaceted chemical and biological activity. The thesis evaluates the lignocellulosic biomass potential of three varieties of sea buckthorn cultivated in Latvia (Maria Bruvele, Tatjana, Botaničeskaja Lubiteļskaja) as a raw material to produce biologically active substances - proanthocyanidins and serotonin. During the extraction of lignocellulosic biomass, the most suitable extractant for the release of target compounds was ethanol-water mixture (1:1 w/w). Development of the most appropriate isolation technique for the target compounds resulted in high purity proanthocyanidins (PACs) (91-94% PACs/DM) and a fraction containing serotonin (28% serotonin/SM). By mutually comparing the composition of twigs extracts collected in spring and autumn, it was found that the biomass of twigs collected in autumn was the most suitable raw material for the production of serotonin and PACs. Since sea buckthorn leaves do not contain PACs and serotonin, separating them increases the yield of target compounds from the biomass of branches by 8–10%. Using LC-UV-ESI-QTOF MS and LC-DADESI-MS/MS analyses, PACs were determined to contain monomer units of catechin, epicatechin, gallocatechin, and epigallocatechin, mainly forming a mixture of type A and type B procyanidins with a degree of polymerization of 2–3. The proven high antioxidant, antibacterial, antifungal, and anti-inflammatory activity of the hydrophilic extracts and target compounds of twigs provides vast application opportunities in various industries: pharmaceuticals, food and feed industry, production of cosmetics and plant protection products, healthcare, and prevention. By performing in vitro analyses, the effect of the target compounds on the activity of digestive enzymes was determined. The fraction containing serotonin showed a catalytic effect on the activity of alpha-amylase and pancreatic lipase, while the opposite effect was observed for proanthocyanidins. The wood residue of sea buckthorn after extraction, as lignocellulosic biomass, is a suitable substrate for the production of fodder additive with the possibility of regulating its digestibility by changing the mass ratio of fodder components. By enriching the residue with micro- and macro minerals, an environmentally friendly soil additive is obtained, which increases the yield of vegetables and grains, additionally improving the quality of the soil. The results of the doctoral thesis are reflected in 8 SCI scientific publications and four peerreviewed scientific conference papers. There is 1 patent of the Republic of Latvia submitted. The research was conducted at the LV Institute of Wood Chemistry, Lignin Chemistry Laboratory in the period from 2020 to 2024.