Effects of Laser Mutagenesis on Microalgae Production and Lipid Accumulation in Two Economically Important Fresh Chlorella Strains under Heterotrophic Conditions

Wei Xing,Fengjie Sun,Qun Shao,Ruihao Zhang,Xiaodong Wang,Chang Wang,Zhengquan Gao,Chunxiao Meng,Kai Cao,Zuoxi Wei,Bingkui Zhu

doi:10.3390/agronomy11050961

Abstract

Microalgae produce a variety of high-value products. Enhancing product contents in microalgal cells is one of the efficient ways to decrease production costs. Improved germplasm and heterotrophic cultivation may enhance microalgae biomass and lipid content. In this study, we investigated the effect of three types of laser irradiation and heterotrophic cultivation on lipid productivity, lipid content, and biomass of two Chlorella strains (i.e., FACHB 9 and FACHB 31). Results showed that the highest biomasses of 4.81 g/L (15.03-fold) and 4.66 g/L (7.32-fold) were obtained in the third generation of FACHB 9 and FACHB 31 induced by a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser for 8 min and 12 min, respectively. The highest lipid contents were 525.6 mg/g (1.67-fold) dry weight (DW) and 780.0 mg/g DW (2.20-fold) in the third and the first generations of FACHB 9 and FACHB 31 induced by Nd:YAG for 8 min and by a helium–neon (He–Ne) laser for 4 min, respectively. The highest lipid productivities of 69.82 ± 3.29 mg/L/d (19.7-fold) and 30.71 ± 3.77 mg/L/d (3.1-fold) were obtained in FACHB 9 and FACHB 31 treated by a semiconductor (SC) laser for 4 min and by a He–Ne laser for 12 min, respectively. Our study suggested that laser mutagenesis is a potential method for screening economically important oleaginous microalgae strains.

Highlights

Human development and societal progress have promoted a rapidly growing reliance on fossil fuel reserves or imported fuel to meet energy demands, creating socio-economic burdens for industrial growth worldwide
Our results showed that laser mutagenesis was efficient to screen two strains of Chlorella to obtain mutants with enhanced accumulation of biomass and lipid contents
In C. vulgaris strain FACHB 9, the highest biomass of 4.81 g/L, the highest lipid contents of 525.6 mg/g dry weight (DW), and the maximum lipid productivity of an increase by 20.7-fold were obtained in the third generation of the laser mutants treated with SC for 0.5 min, with

Summary

Introduction

Human development and societal progress have promoted a rapidly growing reliance on fossil fuel reserves or imported fuel to meet energy demands, creating socio-economic burdens for industrial growth worldwide. Biofuel products have attracted increasing attention due to the gradually depleting fossil reserves in addition to the global environmental pollution and political conflicts. Microalgae have been identified as potential candidates for biodiesel industries due to their high biomass production and fast growth [1]. Microalgae have attracted considerable interest among scientists and policymakers due to the increasing demand for an alternative source of renewable energy to replace fossil fuels. The high cost of producing algal oil has led to the generation of the concept of “microalgae biorefinery,” where high-value compounds and biofuels could be produced to make industrial businesses economically feasible [4]

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