Co-culturing microalgae chlorella vulgaris with plant-growth-promoting bacteria: Effects on biomass yield and biochemical composition

Date of Publication

11-2025

Document Type

Bachelor's Thesis

Degree Name

Bachelor of Science in Biology major in Molecular Biology and Biotechnology

Subject Categories

Molecular Biology

College

College of Science

Department/Unit

Biology

Thesis Advisor

Ma. Carmen A. Lagman
Raymond Vincent F. Castillo

Defense Panel Chair

Mark Christian F. Redillas

Defense Panel Member

Florabelle D. Querubin
Andres Philip Mayol

Abstract (English)

Chlorella vulgaris is an excellent source of value-added products, including pigments, proteins, and bioactive compounds. Despite this, challenges such as contamination and nutrient inefficiencies, common in open-pond cultivation, which lower biomass quality and productivity, continue to impede further commercial development. Microalgae-bacteria co-culture has shown promise as a sustainable strategy to enhance biomass production, biochemical composition, and culture stability for various biotechnological applications. This study investigates the effects of co-culturing C. vulgaris with plant-growth-promoting bacteria (PGPB) on biomass yield and biochemical composition of the microalgae. C. vulgaris was cultured under monoculture and co-culture conditions in a 10:1 microalgae-bacteria ratio with three PGPB, and parameters such as dry cell weight (DCW), chlorophyll a, carotenoid concentration, and protein content were measured using filtration, drying, and spectrophotometric methods. Co-cultures with Bacillus subtilis and Bacillus thuringiensis produced significantly higher biomass and productivity (~5% and ~10%, respectively) compared to the monoculture, while chlorophyll a, carotenoid, and protein contents showed no significant changes. These results may indicate a shift toward the accumulation of non-pigmented storage compounds such as lipids or carbohydrates, warranting further investigation. In contrast, co-culture with P. polymyxa resulted in a significant biomass, pigment, and protein reduction, suggesting strain and method-specific inhibitory interactions. Results demonstrate that co-culturing C. vulgaris with B. subtilis and B. thuringiensis can enhance or maintain algal productivity without adverse effects, highlighting its potential for stable and efficient microalgal cultivation for various bioresource applications. This study represents the first investigation into the effects of co-culturing Chlorella vulgaris under non-immobilized and mixotrophic conditions with the specific plant-growth-promoting bacteria B. subtilis, B. thuringiensis, and P. polymyxa.

Abstract Format

html

Abstract (Filipino)

Ang Chlorella vulgaris ay isang mainam na mapagkukunan ng mga value-added products, katulad ng mga pigment, protina, at mga bioactive compound. Subalit, ang mga hamon tulad ng kontaminasyon at hindi mabisang paggamit ng nutrisyon, na karaniwan sa open-pond cultivation at nagpapababa ng kalidad ng biomass at produktibidad, ay patuloy na humahadlang sa mas malawak na komersyal na pag-unlad nito. Nagpakita ang microalgae-bacteria co-culture ng potensyal bilang isang estratehiya upang mapabuti ang produksyon ng biomass, komposisyong biochemical, at culture stability para sa iba't ibang aplikasyong biotechnolohical. Ang pag-aaral na ito ay nagsisiyasat sa mga epekto ng co-culturing ng C. vulgaris kasama ang mga plant-growth-promoting bacteria (PGPB) sa dami ng biomass at komposisyong biochemical ng microalgae. Pinalaki ang C.vulgaris sa ilalim ng mga kondisyong monoculture at co-culture sa ratio na 10:1 (microalgae-bacteria) kasama ang tatlong PGPB. Sinukat ang mga parametro tulad ng dry cell weight (DCW), chlorophyll a, konsentrasyon ng carotenoid, at nilalaman ng protina gamit ang filtration, drying, at spectrophotometric methods. Ang mga co-culture kasama ang Bacillus subtilis at Bacillus thuringiensis ay nagpakita ng mas mataas na biomass at produktibidad (~5% at ~10% ayon sa pagkakabanggit) kumpara sa monoculture, habang ang nilalaman na chlorophyll a, carotenoid, at protina ay hindi nagpakita ng signipikong pagbabago. Ang mga resultang ito ay maaaring maghimaton ng isang paglipat patungo sa akumulasyon ng mga non-pigmented storage compounds tulad ng lipid o carbohydrate, na nangangailangan ng karagdagang imbestigasyon. Ang co-culture kasama ang P. polymyxa ay nagresulta naman sa makabuluhang pagbaba ng biomass, pigment, at protina, na nagmumungkahi ng mga strain at method-specific inhibitory interactions. Ipinapakita ng mga resulta na ang co-culturing ng C. vulgaris kasama ang B. subtilis at B. thuringiensis ay maaaring mapabuti o mapanatili ang algal productivity nang walang masamang epekto, na nagbibigay-diin sa potensyal nito para sa matatag at episyenteng microalgal cultivation para sa iba't ibang aplikasyon ng bioresource. Ang pag-aaral na ito ay kumakatawan sa unang imbestigasyon sa mga epekto ng co-culturing ng Chlorella vulgaris sa ilalim ng mga kondisyong non-immobilized at mixotrophic kasama ang mga tiyak na plant-growth-promoting bacteria na B. subtilis, B. thuringiensis, at P. polymyxa.

Abstract Format

html

Language

English

Format

Electronic

Keywords

Plant growth-promoting rhizobacteria; Microalgae; Biomass

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Embargo Period

12-10-2025

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