Title Optimizacija proizvodnje polihidroksialkanoata iz otpadne biomase Title (english) Optimization of polyhydroxyalkanoate production from waste biomass Author Karlo Grgurević Mentor Dajana Kučić Grgić (mentor)Committee member Dajana Kučić Grgić (predsjednik povjerenstva)Committee member Vesna Ocelić Bulatović (član povjerenstva)Committee member Martina Miloloža (član povjerenstva)Granter University of Zagreb Defense date and country 2024-09-02, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Plastika nastala iz nafte i naftnih derivata danas je jedan od najkorištenijih materijala u svakodnevnom životu ljudi. Međutim, uslijed njene sve veće proizvodnje, javlja se problem njene toksičnosti, adekvatnog odlaganja i akumulacije u okolišu. Iz tog razloga istražuju se nove vrste biorazgradive plastike s ciljem zamjene za sintetičku. Jedna od biorazgradivih vrsta plastike jesu polihidroksialkanoati, PHA. PHA su specifični zbog načina njihove sinteze i potpuno biorazgradive prirode. Naime, PHA se mogu proizvesti jedino metaboličkim procesima mikroorganizama. Ukoliko se mikroorganizmima pruži supstrat s manjkom dušika i velikim viškom ugljika, mikroorganizmi će početi proizvoditi PHA kao rezervni izvor energije. Kao potencijalni supstrat koji bi se mogao koristiti u te svrhe, u posljednje vrijeme sagledava se agroindustrijski otpad. Korištenjem agroindustrijskog otpada za proizvodnju PHA smanjila bi se količina samog otpada, a ujedno bi se proizveo novi i održivi materijal. Takav proces bi se potencijalno mogao implementirati u industrijske procese, čime bi se zadovoljili zahtjevi kružne ekonomije, a ujedno bi se povoljno utjecalo na okoliš. Međutim, agroindustrijski otpad zahtjeva adekvatnu predobradu kako bi postao povoljan supstrat za proizvodnju PHA.
U ovom radu ispitala se predobrada otpadnog škroba ultrazvukom, mijenjajući tri čimbenika, a to su vrijeme, jačina ultrazvuka i koncentracija otopine NaOH. Iz škroba su izolirane
4 bakterije: Leukonostoc sp., Citrobacter freundii, Staphilococcus lentus i Bacillus licheniformis te 3 gljive: Cryptococcus humicola, Geotrichum klebahnii i Candida krusei sa sposobnošću proizvodnje PHA. Isti su mikroorganizmi korišteni u procesu fermentacije na čvrstom nosaču (eng. Solid State Fermentation, SSF) kako bi se proizveo PHA. Rezultati su pokazali vrijednosti akumulacije PHA ne veće od 1 %, među kojima je najveća vrijednost 0,5572 % pri uvjetima predobrade škroba od 30 minuta, 2 W mL^-1 te koncentraciji NaOH od
0,01 mol L^-1. Generalno, što su uvjeti predobrade škroba bili većih vrijednosti (dulje vrijeme predobrade, veća jačina ultrazvuka te veća koncentracija otopine NaOH), to je akumulacija PHA bila manja. Infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR), diferencijalnom pretražnom kalorimetrijom (DSC) te termogravimetrijskom analizom (TGA) utvrđeno je kako bi se potencijalno moglo raditi o PHB i PHV homopolimerima te kopolimerima PHBV s različitim udjelima HB i HV te kopolimerima s raznim kratkolančanim i srednjelančanim PHA.
Abstract (english) Nowadays, plastic made from oil and oil derivatives is one of the most used materials in people's daily lives. However, due to its increasing production, a problem of its toxicity, adequate disposal and accumulation in the environment is arising. For this reason, scientific research is aimed towards new types of biodegradable plastics in order to replace the synthetic ones. One of the biodegradable types are polyhydroxyalkanoates, PHA. PHAs are specific because of their synthesis method and their completely biodegradable nature.
They can only be produced by metabolic processes of microorganisms. If microorganisms are provided with a substrate with nitrogen deficiency and a large excess of carbon, the microorganisms will start producing PHA as a reserve energy source. Recently,
agro-industrial waste has been considered as a potential substrate that could be used for these purposes. By using agro-industrial waste to produce PHA, the amount of waste itself would be reduced, and at the same time a new and sustainable material would be produced. Such process could potentially be implemented in industrial infrastructure, which could meet the requirements of the circular economy, whilst at the same time have a favorable impact on the environment. However, agro-industrial waste requires adequate pretreatment in order to become a favorable substrate for PHA production. In this paper, an ultrasound pretreatment of waste starch was examined by changing three factors, the time of ultrasonic treatment, the ultrasonic power and the concentration of the NaOH solution. Four bacteria were isolated from starch: Leukonostoc sp., Citrobacter freundii, Staphilococcus lentus and Bacillus licheniformis and three fungi: Cryptococcus humicola, Geotrichum klebahnii and Candida krusei. All of them can produce PHA. The same microorganisms were used in the solid-state fermentation process, SSF, to produce PHA. The results showed values of PHA accumulation not higher than 1%, among which the highest value was 0,5572% under starch pretreatment conditions of 30 minutes, 2 W mL^-1 and 0,01 mol L^-1. In general, results have shown that stronger starch pretreatment conditions (longer pretreatment, higher ultrasound power and higher concentration of NaOH solution) result with lower PHA accumulation. Fourier transformation infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA) showed that synthesized PHA polymers could potentially be PHB and PHV homopolymers, PHBV copolymers with different HB and HV proportions or copolymers made of various short-chain-length and medium-chain-length PHAs.
Keywords
polihidroksialkanoat (PHA)
otpadni škrob
predobrada
fermentacija
akumulacija PHA
Keywords (english)
polyhydroxyalkanoate (PHA)
waste starch
pretreatment
fermentation
PHA accumulation
Language croatian URN:NBN urn:nbn:hr:149:764113 Project Number: NPOO.C3.2.R3-I1.04.0059 Study programme Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry Type of resource Text File origin Born digital Access conditions Embargoed access Terms of use Created on 2024-09-10 11:56:38
